src/HOL/Limits.thy
author blanchet
Wed Feb 12 08:35:57 2014 +0100 (2014-02-12)
changeset 55415 05f5fdb8d093
parent 54863 82acc20ded73
child 56330 5c4d3be7a6b0
permissions -rw-r--r--
renamed 'nat_{case,rec}' to '{case,rec}_nat'
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(*  Title:      HOL/Limits.thy
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    Author:     Brian Huffman
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    Author:     Jacques D. Fleuriot, University of Cambridge
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    Author:     Lawrence C Paulson
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    Author:     Jeremy Avigad
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*)
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header {* Limits on Real Vector Spaces *}
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theory Limits
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imports Real_Vector_Spaces
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begin
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subsection {* Filter going to infinity norm *}
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definition at_infinity :: "'a::real_normed_vector filter" where
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  "at_infinity = Abs_filter (\<lambda>P. \<exists>r. \<forall>x. r \<le> norm x \<longrightarrow> P x)"
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lemma eventually_at_infinity:
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  "eventually P at_infinity \<longleftrightarrow> (\<exists>b. \<forall>x. b \<le> norm x \<longrightarrow> P x)"
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unfolding at_infinity_def
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proof (rule eventually_Abs_filter, rule is_filter.intro)
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  fix P Q :: "'a \<Rightarrow> bool"
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  assume "\<exists>r. \<forall>x. r \<le> norm x \<longrightarrow> P x" and "\<exists>s. \<forall>x. s \<le> norm x \<longrightarrow> Q x"
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  then obtain r s where
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    "\<forall>x. r \<le> norm x \<longrightarrow> P x" and "\<forall>x. s \<le> norm x \<longrightarrow> Q x" by auto
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  then have "\<forall>x. max r s \<le> norm x \<longrightarrow> P x \<and> Q x" by simp
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  then show "\<exists>r. \<forall>x. r \<le> norm x \<longrightarrow> P x \<and> Q x" ..
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qed auto
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lemma at_infinity_eq_at_top_bot:
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  "(at_infinity \<Colon> real filter) = sup at_top at_bot"
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  unfolding sup_filter_def at_infinity_def eventually_at_top_linorder eventually_at_bot_linorder
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proof (intro arg_cong[where f=Abs_filter] ext iffI)
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  fix P :: "real \<Rightarrow> bool"
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  assume "\<exists>r. \<forall>x. r \<le> norm x \<longrightarrow> P x"
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  then obtain r where "\<forall>x. r \<le> norm x \<longrightarrow> P x" ..
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  then have "(\<forall>x\<ge>r. P x) \<and> (\<forall>x\<le>-r. P x)" by auto
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  then show "(\<exists>r. \<forall>x\<ge>r. P x) \<and> (\<exists>r. \<forall>x\<le>r. P x)" by auto
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next
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  fix P :: "real \<Rightarrow> bool"
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  assume "(\<exists>r. \<forall>x\<ge>r. P x) \<and> (\<exists>r. \<forall>x\<le>r. P x)"
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  then obtain p q where "\<forall>x\<ge>p. P x" "\<forall>x\<le>q. P x" by auto
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  then show "\<exists>r. \<forall>x. r \<le> norm x \<longrightarrow> P x"
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    by (intro exI[of _ "max p (-q)"]) (auto simp: abs_real_def)
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qed
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lemma at_top_le_at_infinity:
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  "at_top \<le> (at_infinity :: real filter)"
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  unfolding at_infinity_eq_at_top_bot by simp
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lemma at_bot_le_at_infinity:
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  "at_bot \<le> (at_infinity :: real filter)"
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  unfolding at_infinity_eq_at_top_bot by simp
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subsubsection {* Boundedness *}
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definition Bfun :: "('a \<Rightarrow> 'b::metric_space) \<Rightarrow> 'a filter \<Rightarrow> bool" where
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  Bfun_metric_def: "Bfun f F = (\<exists>y. \<exists>K>0. eventually (\<lambda>x. dist (f x) y \<le> K) F)"
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abbreviation Bseq :: "(nat \<Rightarrow> 'a::metric_space) \<Rightarrow> bool" where
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  "Bseq X \<equiv> Bfun X sequentially"
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lemma Bseq_conv_Bfun: "Bseq X \<longleftrightarrow> Bfun X sequentially" ..
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lemma Bseq_ignore_initial_segment: "Bseq X \<Longrightarrow> Bseq (\<lambda>n. X (n + k))"
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  unfolding Bfun_metric_def by (subst eventually_sequentially_seg)
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lemma Bseq_offset: "Bseq (\<lambda>n. X (n + k)) \<Longrightarrow> Bseq X"
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  unfolding Bfun_metric_def by (subst (asm) eventually_sequentially_seg)
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lemma Bfun_def:
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  "Bfun f F \<longleftrightarrow> (\<exists>K>0. eventually (\<lambda>x. norm (f x) \<le> K) F)"
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  unfolding Bfun_metric_def norm_conv_dist
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proof safe
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  fix y K assume "0 < K" and *: "eventually (\<lambda>x. dist (f x) y \<le> K) F"
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  moreover have "eventually (\<lambda>x. dist (f x) 0 \<le> dist (f x) y + dist 0 y) F"
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    by (intro always_eventually) (metis dist_commute dist_triangle)
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  with * have "eventually (\<lambda>x. dist (f x) 0 \<le> K + dist 0 y) F"
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    by eventually_elim auto
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  with `0 < K` show "\<exists>K>0. eventually (\<lambda>x. dist (f x) 0 \<le> K) F"
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    by (intro exI[of _ "K + dist 0 y"] add_pos_nonneg conjI zero_le_dist) auto
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qed auto
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lemma BfunI:
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  assumes K: "eventually (\<lambda>x. norm (f x) \<le> K) F" shows "Bfun f F"
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unfolding Bfun_def
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proof (intro exI conjI allI)
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  show "0 < max K 1" by simp
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next
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  show "eventually (\<lambda>x. norm (f x) \<le> max K 1) F"
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    using K by (rule eventually_elim1, simp)
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qed
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lemma BfunE:
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  assumes "Bfun f F"
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  obtains B where "0 < B" and "eventually (\<lambda>x. norm (f x) \<le> B) F"
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using assms unfolding Bfun_def by fast
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lemma Cauchy_Bseq: "Cauchy X \<Longrightarrow> Bseq X"
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  unfolding Cauchy_def Bfun_metric_def eventually_sequentially
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  apply (erule_tac x=1 in allE)
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  apply simp
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  apply safe
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  apply (rule_tac x="X M" in exI)
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  apply (rule_tac x=1 in exI)
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  apply (erule_tac x=M in allE)
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  apply simp
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  apply (rule_tac x=M in exI)
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  apply (auto simp: dist_commute)
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  done
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subsubsection {* Bounded Sequences *}
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lemma BseqI': "(\<And>n. norm (X n) \<le> K) \<Longrightarrow> Bseq X"
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  by (intro BfunI) (auto simp: eventually_sequentially)
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lemma BseqI2': "\<forall>n\<ge>N. norm (X n) \<le> K \<Longrightarrow> Bseq X"
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  by (intro BfunI) (auto simp: eventually_sequentially)
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lemma Bseq_def: "Bseq X \<longleftrightarrow> (\<exists>K>0. \<forall>n. norm (X n) \<le> K)"
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  unfolding Bfun_def eventually_sequentially
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proof safe
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  fix N K assume "0 < K" "\<forall>n\<ge>N. norm (X n) \<le> K"
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  then show "\<exists>K>0. \<forall>n. norm (X n) \<le> K"
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    by (intro exI[of _ "max (Max (norm ` X ` {..N})) K"] max.strict_coboundedI2)
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       (auto intro!: imageI not_less[where 'a=nat, THEN iffD1] Max_ge simp: le_max_iff_disj)
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qed auto
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lemma BseqE: "\<lbrakk>Bseq X; \<And>K. \<lbrakk>0 < K; \<forall>n. norm (X n) \<le> K\<rbrakk> \<Longrightarrow> Q\<rbrakk> \<Longrightarrow> Q"
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unfolding Bseq_def by auto
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lemma BseqD: "Bseq X ==> \<exists>K. 0 < K & (\<forall>n. norm (X n) \<le> K)"
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by (simp add: Bseq_def)
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lemma BseqI: "[| 0 < K; \<forall>n. norm (X n) \<le> K |] ==> Bseq X"
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by (auto simp add: Bseq_def)
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lemma Bseq_bdd_above: "Bseq (X::nat \<Rightarrow> real) \<Longrightarrow> bdd_above (range X)"
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proof (elim BseqE, intro bdd_aboveI2)
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  fix K n assume "0 < K" "\<forall>n. norm (X n) \<le> K" then show "X n \<le> K"
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    by (auto elim!: allE[of _ n])
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qed
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lemma Bseq_bdd_below: "Bseq (X::nat \<Rightarrow> real) \<Longrightarrow> bdd_below (range X)"
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proof (elim BseqE, intro bdd_belowI2)
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  fix K n assume "0 < K" "\<forall>n. norm (X n) \<le> K" then show "- K \<le> X n"
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    by (auto elim!: allE[of _ n])
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qed
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lemma lemma_NBseq_def:
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  "(\<exists>K > 0. \<forall>n. norm (X n) \<le> K) = (\<exists>N. \<forall>n. norm (X n) \<le> real(Suc N))"
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proof safe
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  fix K :: real
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  from reals_Archimedean2 obtain n :: nat where "K < real n" ..
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  then have "K \<le> real (Suc n)" by auto
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  moreover assume "\<forall>m. norm (X m) \<le> K"
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  ultimately have "\<forall>m. norm (X m) \<le> real (Suc n)"
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    by (blast intro: order_trans)
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  then show "\<exists>N. \<forall>n. norm (X n) \<le> real (Suc N)" ..
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qed (force simp add: real_of_nat_Suc)
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text{* alternative definition for Bseq *}
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lemma Bseq_iff: "Bseq X = (\<exists>N. \<forall>n. norm (X n) \<le> real(Suc N))"
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apply (simp add: Bseq_def)
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apply (simp (no_asm) add: lemma_NBseq_def)
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done
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lemma lemma_NBseq_def2:
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     "(\<exists>K > 0. \<forall>n. norm (X n) \<le> K) = (\<exists>N. \<forall>n. norm (X n) < real(Suc N))"
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apply (subst lemma_NBseq_def, auto)
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apply (rule_tac x = "Suc N" in exI)
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apply (rule_tac [2] x = N in exI)
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apply (auto simp add: real_of_nat_Suc)
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 prefer 2 apply (blast intro: order_less_imp_le)
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apply (drule_tac x = n in spec, simp)
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done
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(* yet another definition for Bseq *)
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lemma Bseq_iff1a: "Bseq X = (\<exists>N. \<forall>n. norm (X n) < real(Suc N))"
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by (simp add: Bseq_def lemma_NBseq_def2)
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subsubsection{*A Few More Equivalence Theorems for Boundedness*}
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text{*alternative formulation for boundedness*}
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lemma Bseq_iff2: "Bseq X = (\<exists>k > 0. \<exists>x. \<forall>n. norm (X(n) + -x) \<le> k)"
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apply (unfold Bseq_def, safe)
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apply (rule_tac [2] x = "k + norm x" in exI)
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apply (rule_tac x = K in exI, simp)
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apply (rule exI [where x = 0], auto)
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apply (erule order_less_le_trans, simp)
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apply (drule_tac x=n in spec)
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apply (drule order_trans [OF norm_triangle_ineq2])
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apply simp
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done
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text{*alternative formulation for boundedness*}
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lemma Bseq_iff3:
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  "Bseq X \<longleftrightarrow> (\<exists>k>0. \<exists>N. \<forall>n. norm (X n + - X N) \<le> k)" (is "?P \<longleftrightarrow> ?Q")
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proof
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  assume ?P
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  then obtain K
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    where *: "0 < K" and **: "\<And>n. norm (X n) \<le> K" by (auto simp add: Bseq_def)
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  from * have "0 < K + norm (X 0)" by (rule order_less_le_trans) simp
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  from ** have "\<forall>n. norm (X n - X 0) \<le> K + norm (X 0)"
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    by (auto intro: order_trans norm_triangle_ineq4)
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  then have "\<forall>n. norm (X n + - X 0) \<le> K + norm (X 0)"
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    by simp
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  with `0 < K + norm (X 0)` show ?Q by blast
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next
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  assume ?Q then show ?P by (auto simp add: Bseq_iff2)
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qed
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lemma BseqI2: "(\<forall>n. k \<le> f n & f n \<le> (K::real)) ==> Bseq f"
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apply (simp add: Bseq_def)
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apply (rule_tac x = " (\<bar>k\<bar> + \<bar>K\<bar>) + 1" in exI, auto)
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apply (drule_tac x = n in spec, arith)
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done
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subsubsection{*Upper Bounds and Lubs of Bounded Sequences*}
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lemma Bseq_minus_iff: "Bseq (%n. -(X n) :: 'a :: real_normed_vector) = Bseq X"
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  by (simp add: Bseq_def)
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lemma Bseq_eq_bounded: "range f \<subseteq> {a .. b::real} \<Longrightarrow> Bseq f"
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  apply (simp add: subset_eq)
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  apply (rule BseqI'[where K="max (norm a) (norm b)"])
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  apply (erule_tac x=n in allE)
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  apply auto
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  done
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lemma incseq_bounded: "incseq X \<Longrightarrow> \<forall>i. X i \<le> (B::real) \<Longrightarrow> Bseq X"
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  by (intro Bseq_eq_bounded[of X "X 0" B]) (auto simp: incseq_def)
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lemma decseq_bounded: "decseq X \<Longrightarrow> \<forall>i. (B::real) \<le> X i \<Longrightarrow> Bseq X"
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  by (intro Bseq_eq_bounded[of X B "X 0"]) (auto simp: decseq_def)
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subsection {* Bounded Monotonic Sequences *}
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subsubsection{*A Bounded and Monotonic Sequence Converges*}
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(* TODO: delete *)
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(* FIXME: one use in NSA/HSEQ.thy *)
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lemma Bmonoseq_LIMSEQ: "\<forall>n. m \<le> n --> X n = X m ==> \<exists>L. (X ----> L)"
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  apply (rule_tac x="X m" in exI)
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  apply (rule filterlim_cong[THEN iffD2, OF refl refl _ tendsto_const])
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  unfolding eventually_sequentially
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  apply blast
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  done
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subsection {* Convergence to Zero *}
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definition Zfun :: "('a \<Rightarrow> 'b::real_normed_vector) \<Rightarrow> 'a filter \<Rightarrow> bool"
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  where "Zfun f F = (\<forall>r>0. eventually (\<lambda>x. norm (f x) < r) F)"
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lemma ZfunI:
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  "(\<And>r. 0 < r \<Longrightarrow> eventually (\<lambda>x. norm (f x) < r) F) \<Longrightarrow> Zfun f F"
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  unfolding Zfun_def by simp
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lemma ZfunD:
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  "\<lbrakk>Zfun f F; 0 < r\<rbrakk> \<Longrightarrow> eventually (\<lambda>x. norm (f x) < r) F"
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  unfolding Zfun_def by simp
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lemma Zfun_ssubst:
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  "eventually (\<lambda>x. f x = g x) F \<Longrightarrow> Zfun g F \<Longrightarrow> Zfun f F"
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  unfolding Zfun_def by (auto elim!: eventually_rev_mp)
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lemma Zfun_zero: "Zfun (\<lambda>x. 0) F"
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  unfolding Zfun_def by simp
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lemma Zfun_norm_iff: "Zfun (\<lambda>x. norm (f x)) F = Zfun (\<lambda>x. f x) F"
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  unfolding Zfun_def by simp
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lemma Zfun_imp_Zfun:
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  assumes f: "Zfun f F"
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   279
  assumes g: "eventually (\<lambda>x. norm (g x) \<le> norm (f x) * K) F"
huffman@44195
   280
  shows "Zfun (\<lambda>x. g x) F"
huffman@31349
   281
proof (cases)
huffman@31349
   282
  assume K: "0 < K"
huffman@31349
   283
  show ?thesis
huffman@31349
   284
  proof (rule ZfunI)
huffman@31349
   285
    fix r::real assume "0 < r"
huffman@31349
   286
    hence "0 < r / K"
huffman@31349
   287
      using K by (rule divide_pos_pos)
huffman@44195
   288
    then have "eventually (\<lambda>x. norm (f x) < r / K) F"
huffman@31487
   289
      using ZfunD [OF f] by fast
huffman@44195
   290
    with g show "eventually (\<lambda>x. norm (g x) < r) F"
noschinl@46887
   291
    proof eventually_elim
noschinl@46887
   292
      case (elim x)
huffman@31487
   293
      hence "norm (f x) * K < r"
huffman@31349
   294
        by (simp add: pos_less_divide_eq K)
noschinl@46887
   295
      thus ?case
noschinl@46887
   296
        by (simp add: order_le_less_trans [OF elim(1)])
huffman@31349
   297
    qed
huffman@31349
   298
  qed
huffman@31349
   299
next
huffman@31349
   300
  assume "\<not> 0 < K"
huffman@31349
   301
  hence K: "K \<le> 0" by (simp only: not_less)
huffman@31355
   302
  show ?thesis
huffman@31355
   303
  proof (rule ZfunI)
huffman@31355
   304
    fix r :: real
huffman@31355
   305
    assume "0 < r"
huffman@44195
   306
    from g show "eventually (\<lambda>x. norm (g x) < r) F"
noschinl@46887
   307
    proof eventually_elim
noschinl@46887
   308
      case (elim x)
noschinl@46887
   309
      also have "norm (f x) * K \<le> norm (f x) * 0"
huffman@31355
   310
        using K norm_ge_zero by (rule mult_left_mono)
noschinl@46887
   311
      finally show ?case
huffman@31355
   312
        using `0 < r` by simp
huffman@31355
   313
    qed
huffman@31355
   314
  qed
huffman@31349
   315
qed
huffman@31349
   316
huffman@44195
   317
lemma Zfun_le: "\<lbrakk>Zfun g F; \<forall>x. norm (f x) \<le> norm (g x)\<rbrakk> \<Longrightarrow> Zfun f F"
huffman@44081
   318
  by (erule_tac K="1" in Zfun_imp_Zfun, simp)
huffman@31349
   319
huffman@31349
   320
lemma Zfun_add:
huffman@44195
   321
  assumes f: "Zfun f F" and g: "Zfun g F"
huffman@44195
   322
  shows "Zfun (\<lambda>x. f x + g x) F"
huffman@31349
   323
proof (rule ZfunI)
huffman@31349
   324
  fix r::real assume "0 < r"
huffman@31349
   325
  hence r: "0 < r / 2" by simp
huffman@44195
   326
  have "eventually (\<lambda>x. norm (f x) < r/2) F"
huffman@31487
   327
    using f r by (rule ZfunD)
huffman@31349
   328
  moreover
huffman@44195
   329
  have "eventually (\<lambda>x. norm (g x) < r/2) F"
huffman@31487
   330
    using g r by (rule ZfunD)
huffman@31349
   331
  ultimately
huffman@44195
   332
  show "eventually (\<lambda>x. norm (f x + g x) < r) F"
noschinl@46887
   333
  proof eventually_elim
noschinl@46887
   334
    case (elim x)
huffman@31487
   335
    have "norm (f x + g x) \<le> norm (f x) + norm (g x)"
huffman@31349
   336
      by (rule norm_triangle_ineq)
huffman@31349
   337
    also have "\<dots> < r/2 + r/2"
noschinl@46887
   338
      using elim by (rule add_strict_mono)
noschinl@46887
   339
    finally show ?case
huffman@31349
   340
      by simp
huffman@31349
   341
  qed
huffman@31349
   342
qed
huffman@31349
   343
huffman@44195
   344
lemma Zfun_minus: "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. - f x) F"
huffman@44081
   345
  unfolding Zfun_def by simp
huffman@31349
   346
huffman@44195
   347
lemma Zfun_diff: "\<lbrakk>Zfun f F; Zfun g F\<rbrakk> \<Longrightarrow> Zfun (\<lambda>x. f x - g x) F"
haftmann@54230
   348
  using Zfun_add [of f F "\<lambda>x. - g x"] by (simp add: Zfun_minus)
huffman@31349
   349
huffman@31349
   350
lemma (in bounded_linear) Zfun:
huffman@44195
   351
  assumes g: "Zfun g F"
huffman@44195
   352
  shows "Zfun (\<lambda>x. f (g x)) F"
huffman@31349
   353
proof -
huffman@31349
   354
  obtain K where "\<And>x. norm (f x) \<le> norm x * K"
huffman@31349
   355
    using bounded by fast
huffman@44195
   356
  then have "eventually (\<lambda>x. norm (f (g x)) \<le> norm (g x) * K) F"
huffman@31355
   357
    by simp
huffman@31487
   358
  with g show ?thesis
huffman@31349
   359
    by (rule Zfun_imp_Zfun)
huffman@31349
   360
qed
huffman@31349
   361
huffman@31349
   362
lemma (in bounded_bilinear) Zfun:
huffman@44195
   363
  assumes f: "Zfun f F"
huffman@44195
   364
  assumes g: "Zfun g F"
huffman@44195
   365
  shows "Zfun (\<lambda>x. f x ** g x) F"
huffman@31349
   366
proof (rule ZfunI)
huffman@31349
   367
  fix r::real assume r: "0 < r"
huffman@31349
   368
  obtain K where K: "0 < K"
huffman@31349
   369
    and norm_le: "\<And>x y. norm (x ** y) \<le> norm x * norm y * K"
huffman@31349
   370
    using pos_bounded by fast
huffman@31349
   371
  from K have K': "0 < inverse K"
huffman@31349
   372
    by (rule positive_imp_inverse_positive)
huffman@44195
   373
  have "eventually (\<lambda>x. norm (f x) < r) F"
huffman@31487
   374
    using f r by (rule ZfunD)
huffman@31349
   375
  moreover
huffman@44195
   376
  have "eventually (\<lambda>x. norm (g x) < inverse K) F"
huffman@31487
   377
    using g K' by (rule ZfunD)
huffman@31349
   378
  ultimately
huffman@44195
   379
  show "eventually (\<lambda>x. norm (f x ** g x) < r) F"
noschinl@46887
   380
  proof eventually_elim
noschinl@46887
   381
    case (elim x)
huffman@31487
   382
    have "norm (f x ** g x) \<le> norm (f x) * norm (g x) * K"
huffman@31349
   383
      by (rule norm_le)
huffman@31487
   384
    also have "norm (f x) * norm (g x) * K < r * inverse K * K"
noschinl@46887
   385
      by (intro mult_strict_right_mono mult_strict_mono' norm_ge_zero elim K)
huffman@31349
   386
    also from K have "r * inverse K * K = r"
huffman@31349
   387
      by simp
noschinl@46887
   388
    finally show ?case .
huffman@31349
   389
  qed
huffman@31349
   390
qed
huffman@31349
   391
huffman@31349
   392
lemma (in bounded_bilinear) Zfun_left:
huffman@44195
   393
  "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. f x ** a) F"
huffman@44081
   394
  by (rule bounded_linear_left [THEN bounded_linear.Zfun])
huffman@31349
   395
huffman@31349
   396
lemma (in bounded_bilinear) Zfun_right:
huffman@44195
   397
  "Zfun f F \<Longrightarrow> Zfun (\<lambda>x. a ** f x) F"
huffman@44081
   398
  by (rule bounded_linear_right [THEN bounded_linear.Zfun])
huffman@31349
   399
huffman@44282
   400
lemmas Zfun_mult = bounded_bilinear.Zfun [OF bounded_bilinear_mult]
huffman@44282
   401
lemmas Zfun_mult_right = bounded_bilinear.Zfun_right [OF bounded_bilinear_mult]
huffman@44282
   402
lemmas Zfun_mult_left = bounded_bilinear.Zfun_left [OF bounded_bilinear_mult]
huffman@31349
   403
huffman@44195
   404
lemma tendsto_Zfun_iff: "(f ---> a) F = Zfun (\<lambda>x. f x - a) F"
huffman@44081
   405
  by (simp only: tendsto_iff Zfun_def dist_norm)
huffman@31349
   406
huffman@44205
   407
subsubsection {* Distance and norms *}
huffman@36662
   408
hoelzl@51531
   409
lemma tendsto_dist [tendsto_intros]:
hoelzl@51531
   410
  fixes l m :: "'a :: metric_space"
hoelzl@51531
   411
  assumes f: "(f ---> l) F" and g: "(g ---> m) F"
hoelzl@51531
   412
  shows "((\<lambda>x. dist (f x) (g x)) ---> dist l m) F"
hoelzl@51531
   413
proof (rule tendstoI)
hoelzl@51531
   414
  fix e :: real assume "0 < e"
hoelzl@51531
   415
  hence e2: "0 < e/2" by simp
hoelzl@51531
   416
  from tendstoD [OF f e2] tendstoD [OF g e2]
hoelzl@51531
   417
  show "eventually (\<lambda>x. dist (dist (f x) (g x)) (dist l m) < e) F"
hoelzl@51531
   418
  proof (eventually_elim)
hoelzl@51531
   419
    case (elim x)
hoelzl@51531
   420
    then show "dist (dist (f x) (g x)) (dist l m) < e"
hoelzl@51531
   421
      unfolding dist_real_def
hoelzl@51531
   422
      using dist_triangle2 [of "f x" "g x" "l"]
hoelzl@51531
   423
      using dist_triangle2 [of "g x" "l" "m"]
hoelzl@51531
   424
      using dist_triangle3 [of "l" "m" "f x"]
hoelzl@51531
   425
      using dist_triangle [of "f x" "m" "g x"]
hoelzl@51531
   426
      by arith
hoelzl@51531
   427
  qed
hoelzl@51531
   428
qed
hoelzl@51531
   429
hoelzl@51531
   430
lemma continuous_dist[continuous_intros]:
hoelzl@51531
   431
  fixes f g :: "_ \<Rightarrow> 'a :: metric_space"
hoelzl@51531
   432
  shows "continuous F f \<Longrightarrow> continuous F g \<Longrightarrow> continuous F (\<lambda>x. dist (f x) (g x))"
hoelzl@51531
   433
  unfolding continuous_def by (rule tendsto_dist)
hoelzl@51531
   434
hoelzl@51531
   435
lemma continuous_on_dist[continuous_on_intros]:
hoelzl@51531
   436
  fixes f g :: "_ \<Rightarrow> 'a :: metric_space"
hoelzl@51531
   437
  shows "continuous_on s f \<Longrightarrow> continuous_on s g \<Longrightarrow> continuous_on s (\<lambda>x. dist (f x) (g x))"
hoelzl@51531
   438
  unfolding continuous_on_def by (auto intro: tendsto_dist)
hoelzl@51531
   439
huffman@31565
   440
lemma tendsto_norm [tendsto_intros]:
huffman@44195
   441
  "(f ---> a) F \<Longrightarrow> ((\<lambda>x. norm (f x)) ---> norm a) F"
huffman@44081
   442
  unfolding norm_conv_dist by (intro tendsto_intros)
huffman@36662
   443
hoelzl@51478
   444
lemma continuous_norm [continuous_intros]:
hoelzl@51478
   445
  "continuous F f \<Longrightarrow> continuous F (\<lambda>x. norm (f x))"
hoelzl@51478
   446
  unfolding continuous_def by (rule tendsto_norm)
hoelzl@51478
   447
hoelzl@51478
   448
lemma continuous_on_norm [continuous_on_intros]:
hoelzl@51478
   449
  "continuous_on s f \<Longrightarrow> continuous_on s (\<lambda>x. norm (f x))"
hoelzl@51478
   450
  unfolding continuous_on_def by (auto intro: tendsto_norm)
hoelzl@51478
   451
huffman@36662
   452
lemma tendsto_norm_zero:
huffman@44195
   453
  "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. norm (f x)) ---> 0) F"
huffman@44081
   454
  by (drule tendsto_norm, simp)
huffman@36662
   455
huffman@36662
   456
lemma tendsto_norm_zero_cancel:
huffman@44195
   457
  "((\<lambda>x. norm (f x)) ---> 0) F \<Longrightarrow> (f ---> 0) F"
huffman@44081
   458
  unfolding tendsto_iff dist_norm by simp
huffman@36662
   459
huffman@36662
   460
lemma tendsto_norm_zero_iff:
huffman@44195
   461
  "((\<lambda>x. norm (f x)) ---> 0) F \<longleftrightarrow> (f ---> 0) F"
huffman@44081
   462
  unfolding tendsto_iff dist_norm by simp
huffman@31349
   463
huffman@44194
   464
lemma tendsto_rabs [tendsto_intros]:
huffman@44195
   465
  "(f ---> (l::real)) F \<Longrightarrow> ((\<lambda>x. \<bar>f x\<bar>) ---> \<bar>l\<bar>) F"
huffman@44194
   466
  by (fold real_norm_def, rule tendsto_norm)
huffman@44194
   467
hoelzl@51478
   468
lemma continuous_rabs [continuous_intros]:
hoelzl@51478
   469
  "continuous F f \<Longrightarrow> continuous F (\<lambda>x. \<bar>f x :: real\<bar>)"
hoelzl@51478
   470
  unfolding real_norm_def[symmetric] by (rule continuous_norm)
hoelzl@51478
   471
hoelzl@51478
   472
lemma continuous_on_rabs [continuous_on_intros]:
hoelzl@51478
   473
  "continuous_on s f \<Longrightarrow> continuous_on s (\<lambda>x. \<bar>f x :: real\<bar>)"
hoelzl@51478
   474
  unfolding real_norm_def[symmetric] by (rule continuous_on_norm)
hoelzl@51478
   475
huffman@44194
   476
lemma tendsto_rabs_zero:
huffman@44195
   477
  "(f ---> (0::real)) F \<Longrightarrow> ((\<lambda>x. \<bar>f x\<bar>) ---> 0) F"
huffman@44194
   478
  by (fold real_norm_def, rule tendsto_norm_zero)
huffman@44194
   479
huffman@44194
   480
lemma tendsto_rabs_zero_cancel:
huffman@44195
   481
  "((\<lambda>x. \<bar>f x\<bar>) ---> (0::real)) F \<Longrightarrow> (f ---> 0) F"
huffman@44194
   482
  by (fold real_norm_def, rule tendsto_norm_zero_cancel)
huffman@44194
   483
huffman@44194
   484
lemma tendsto_rabs_zero_iff:
huffman@44195
   485
  "((\<lambda>x. \<bar>f x\<bar>) ---> (0::real)) F \<longleftrightarrow> (f ---> 0) F"
huffman@44194
   486
  by (fold real_norm_def, rule tendsto_norm_zero_iff)
huffman@44194
   487
huffman@44194
   488
subsubsection {* Addition and subtraction *}
huffman@44194
   489
huffman@31565
   490
lemma tendsto_add [tendsto_intros]:
huffman@31349
   491
  fixes a b :: "'a::real_normed_vector"
huffman@44195
   492
  shows "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x + g x) ---> a + b) F"
huffman@44081
   493
  by (simp only: tendsto_Zfun_iff add_diff_add Zfun_add)
huffman@31349
   494
hoelzl@51478
   495
lemma continuous_add [continuous_intros]:
hoelzl@51478
   496
  fixes f g :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   497
  shows "continuous F f \<Longrightarrow> continuous F g \<Longrightarrow> continuous F (\<lambda>x. f x + g x)"
hoelzl@51478
   498
  unfolding continuous_def by (rule tendsto_add)
hoelzl@51478
   499
hoelzl@51478
   500
lemma continuous_on_add [continuous_on_intros]:
hoelzl@51478
   501
  fixes f g :: "_ \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   502
  shows "continuous_on s f \<Longrightarrow> continuous_on s g \<Longrightarrow> continuous_on s (\<lambda>x. f x + g x)"
hoelzl@51478
   503
  unfolding continuous_on_def by (auto intro: tendsto_add)
hoelzl@51478
   504
huffman@44194
   505
lemma tendsto_add_zero:
hoelzl@51478
   506
  fixes f g :: "_ \<Rightarrow> 'b::real_normed_vector"
huffman@44195
   507
  shows "\<lbrakk>(f ---> 0) F; (g ---> 0) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x + g x) ---> 0) F"
huffman@44194
   508
  by (drule (1) tendsto_add, simp)
huffman@44194
   509
huffman@31565
   510
lemma tendsto_minus [tendsto_intros]:
huffman@31349
   511
  fixes a :: "'a::real_normed_vector"
huffman@44195
   512
  shows "(f ---> a) F \<Longrightarrow> ((\<lambda>x. - f x) ---> - a) F"
huffman@44081
   513
  by (simp only: tendsto_Zfun_iff minus_diff_minus Zfun_minus)
huffman@31349
   514
hoelzl@51478
   515
lemma continuous_minus [continuous_intros]:
hoelzl@51478
   516
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   517
  shows "continuous F f \<Longrightarrow> continuous F (\<lambda>x. - f x)"
hoelzl@51478
   518
  unfolding continuous_def by (rule tendsto_minus)
hoelzl@51478
   519
hoelzl@51478
   520
lemma continuous_on_minus [continuous_on_intros]:
hoelzl@51478
   521
  fixes f :: "_ \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   522
  shows "continuous_on s f \<Longrightarrow> continuous_on s (\<lambda>x. - f x)"
hoelzl@51478
   523
  unfolding continuous_on_def by (auto intro: tendsto_minus)
hoelzl@51478
   524
huffman@31349
   525
lemma tendsto_minus_cancel:
huffman@31349
   526
  fixes a :: "'a::real_normed_vector"
huffman@44195
   527
  shows "((\<lambda>x. - f x) ---> - a) F \<Longrightarrow> (f ---> a) F"
huffman@44081
   528
  by (drule tendsto_minus, simp)
huffman@31349
   529
hoelzl@50330
   530
lemma tendsto_minus_cancel_left:
hoelzl@50330
   531
    "(f ---> - (y::_::real_normed_vector)) F \<longleftrightarrow> ((\<lambda>x. - f x) ---> y) F"
hoelzl@50330
   532
  using tendsto_minus_cancel[of f "- y" F]  tendsto_minus[of f "- y" F]
hoelzl@50330
   533
  by auto
hoelzl@50330
   534
huffman@31565
   535
lemma tendsto_diff [tendsto_intros]:
huffman@31349
   536
  fixes a b :: "'a::real_normed_vector"
huffman@44195
   537
  shows "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x - g x) ---> a - b) F"
haftmann@54230
   538
  using tendsto_add [of f a F "\<lambda>x. - g x" "- b"] by (simp add: tendsto_minus)
huffman@31349
   539
hoelzl@51478
   540
lemma continuous_diff [continuous_intros]:
hoelzl@51478
   541
  fixes f g :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   542
  shows "continuous F f \<Longrightarrow> continuous F g \<Longrightarrow> continuous F (\<lambda>x. f x - g x)"
hoelzl@51478
   543
  unfolding continuous_def by (rule tendsto_diff)
hoelzl@51478
   544
hoelzl@51478
   545
lemma continuous_on_diff [continuous_on_intros]:
hoelzl@51478
   546
  fixes f g :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   547
  shows "continuous_on s f \<Longrightarrow> continuous_on s g \<Longrightarrow> continuous_on s (\<lambda>x. f x - g x)"
hoelzl@51478
   548
  unfolding continuous_on_def by (auto intro: tendsto_diff)
hoelzl@51478
   549
huffman@31588
   550
lemma tendsto_setsum [tendsto_intros]:
huffman@31588
   551
  fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'c::real_normed_vector"
huffman@44195
   552
  assumes "\<And>i. i \<in> S \<Longrightarrow> (f i ---> a i) F"
huffman@44195
   553
  shows "((\<lambda>x. \<Sum>i\<in>S. f i x) ---> (\<Sum>i\<in>S. a i)) F"
huffman@31588
   554
proof (cases "finite S")
huffman@31588
   555
  assume "finite S" thus ?thesis using assms
huffman@44194
   556
    by (induct, simp add: tendsto_const, simp add: tendsto_add)
huffman@31588
   557
next
huffman@31588
   558
  assume "\<not> finite S" thus ?thesis
huffman@31588
   559
    by (simp add: tendsto_const)
huffman@31588
   560
qed
huffman@31588
   561
hoelzl@51478
   562
lemma continuous_setsum [continuous_intros]:
hoelzl@51478
   563
  fixes f :: "'a \<Rightarrow> 'b::t2_space \<Rightarrow> 'c::real_normed_vector"
hoelzl@51478
   564
  shows "(\<And>i. i \<in> S \<Longrightarrow> continuous F (f i)) \<Longrightarrow> continuous F (\<lambda>x. \<Sum>i\<in>S. f i x)"
hoelzl@51478
   565
  unfolding continuous_def by (rule tendsto_setsum)
hoelzl@51478
   566
hoelzl@51478
   567
lemma continuous_on_setsum [continuous_intros]:
hoelzl@51478
   568
  fixes f :: "'a \<Rightarrow> _ \<Rightarrow> 'c::real_normed_vector"
hoelzl@51478
   569
  shows "(\<And>i. i \<in> S \<Longrightarrow> continuous_on s (f i)) \<Longrightarrow> continuous_on s (\<lambda>x. \<Sum>i\<in>S. f i x)"
hoelzl@51478
   570
  unfolding continuous_on_def by (auto intro: tendsto_setsum)
hoelzl@51478
   571
hoelzl@50999
   572
lemmas real_tendsto_sandwich = tendsto_sandwich[where 'b=real]
hoelzl@50999
   573
huffman@44194
   574
subsubsection {* Linear operators and multiplication *}
huffman@44194
   575
huffman@44282
   576
lemma (in bounded_linear) tendsto:
huffman@44195
   577
  "(g ---> a) F \<Longrightarrow> ((\<lambda>x. f (g x)) ---> f a) F"
huffman@44081
   578
  by (simp only: tendsto_Zfun_iff diff [symmetric] Zfun)
huffman@31349
   579
hoelzl@51478
   580
lemma (in bounded_linear) continuous:
hoelzl@51478
   581
  "continuous F g \<Longrightarrow> continuous F (\<lambda>x. f (g x))"
hoelzl@51478
   582
  using tendsto[of g _ F] by (auto simp: continuous_def)
hoelzl@51478
   583
hoelzl@51478
   584
lemma (in bounded_linear) continuous_on:
hoelzl@51478
   585
  "continuous_on s g \<Longrightarrow> continuous_on s (\<lambda>x. f (g x))"
hoelzl@51478
   586
  using tendsto[of g] by (auto simp: continuous_on_def)
hoelzl@51478
   587
huffman@44194
   588
lemma (in bounded_linear) tendsto_zero:
huffman@44195
   589
  "(g ---> 0) F \<Longrightarrow> ((\<lambda>x. f (g x)) ---> 0) F"
huffman@44194
   590
  by (drule tendsto, simp only: zero)
huffman@44194
   591
huffman@44282
   592
lemma (in bounded_bilinear) tendsto:
huffman@44195
   593
  "\<lbrakk>(f ---> a) F; (g ---> b) F\<rbrakk> \<Longrightarrow> ((\<lambda>x. f x ** g x) ---> a ** b) F"
huffman@44081
   594
  by (simp only: tendsto_Zfun_iff prod_diff_prod
huffman@44081
   595
                 Zfun_add Zfun Zfun_left Zfun_right)
huffman@31349
   596
hoelzl@51478
   597
lemma (in bounded_bilinear) continuous:
hoelzl@51478
   598
  "continuous F f \<Longrightarrow> continuous F g \<Longrightarrow> continuous F (\<lambda>x. f x ** g x)"
hoelzl@51478
   599
  using tendsto[of f _ F g] by (auto simp: continuous_def)
hoelzl@51478
   600
hoelzl@51478
   601
lemma (in bounded_bilinear) continuous_on:
hoelzl@51478
   602
  "continuous_on s f \<Longrightarrow> continuous_on s g \<Longrightarrow> continuous_on s (\<lambda>x. f x ** g x)"
hoelzl@51478
   603
  using tendsto[of f _ _ g] by (auto simp: continuous_on_def)
hoelzl@51478
   604
huffman@44194
   605
lemma (in bounded_bilinear) tendsto_zero:
huffman@44195
   606
  assumes f: "(f ---> 0) F"
huffman@44195
   607
  assumes g: "(g ---> 0) F"
huffman@44195
   608
  shows "((\<lambda>x. f x ** g x) ---> 0) F"
huffman@44194
   609
  using tendsto [OF f g] by (simp add: zero_left)
huffman@31355
   610
huffman@44194
   611
lemma (in bounded_bilinear) tendsto_left_zero:
huffman@44195
   612
  "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. f x ** c) ---> 0) F"
huffman@44194
   613
  by (rule bounded_linear.tendsto_zero [OF bounded_linear_left])
huffman@44194
   614
huffman@44194
   615
lemma (in bounded_bilinear) tendsto_right_zero:
huffman@44195
   616
  "(f ---> 0) F \<Longrightarrow> ((\<lambda>x. c ** f x) ---> 0) F"
huffman@44194
   617
  by (rule bounded_linear.tendsto_zero [OF bounded_linear_right])
huffman@44194
   618
huffman@44282
   619
lemmas tendsto_of_real [tendsto_intros] =
huffman@44282
   620
  bounded_linear.tendsto [OF bounded_linear_of_real]
huffman@44282
   621
huffman@44282
   622
lemmas tendsto_scaleR [tendsto_intros] =
huffman@44282
   623
  bounded_bilinear.tendsto [OF bounded_bilinear_scaleR]
huffman@44282
   624
huffman@44282
   625
lemmas tendsto_mult [tendsto_intros] =
huffman@44282
   626
  bounded_bilinear.tendsto [OF bounded_bilinear_mult]
huffman@44194
   627
hoelzl@51478
   628
lemmas continuous_of_real [continuous_intros] =
hoelzl@51478
   629
  bounded_linear.continuous [OF bounded_linear_of_real]
hoelzl@51478
   630
hoelzl@51478
   631
lemmas continuous_scaleR [continuous_intros] =
hoelzl@51478
   632
  bounded_bilinear.continuous [OF bounded_bilinear_scaleR]
hoelzl@51478
   633
hoelzl@51478
   634
lemmas continuous_mult [continuous_intros] =
hoelzl@51478
   635
  bounded_bilinear.continuous [OF bounded_bilinear_mult]
hoelzl@51478
   636
hoelzl@51478
   637
lemmas continuous_on_of_real [continuous_on_intros] =
hoelzl@51478
   638
  bounded_linear.continuous_on [OF bounded_linear_of_real]
hoelzl@51478
   639
hoelzl@51478
   640
lemmas continuous_on_scaleR [continuous_on_intros] =
hoelzl@51478
   641
  bounded_bilinear.continuous_on [OF bounded_bilinear_scaleR]
hoelzl@51478
   642
hoelzl@51478
   643
lemmas continuous_on_mult [continuous_on_intros] =
hoelzl@51478
   644
  bounded_bilinear.continuous_on [OF bounded_bilinear_mult]
hoelzl@51478
   645
huffman@44568
   646
lemmas tendsto_mult_zero =
huffman@44568
   647
  bounded_bilinear.tendsto_zero [OF bounded_bilinear_mult]
huffman@44568
   648
huffman@44568
   649
lemmas tendsto_mult_left_zero =
huffman@44568
   650
  bounded_bilinear.tendsto_left_zero [OF bounded_bilinear_mult]
huffman@44568
   651
huffman@44568
   652
lemmas tendsto_mult_right_zero =
huffman@44568
   653
  bounded_bilinear.tendsto_right_zero [OF bounded_bilinear_mult]
huffman@44568
   654
huffman@44194
   655
lemma tendsto_power [tendsto_intros]:
huffman@44194
   656
  fixes f :: "'a \<Rightarrow> 'b::{power,real_normed_algebra}"
huffman@44195
   657
  shows "(f ---> a) F \<Longrightarrow> ((\<lambda>x. f x ^ n) ---> a ^ n) F"
huffman@44194
   658
  by (induct n) (simp_all add: tendsto_const tendsto_mult)
huffman@44194
   659
hoelzl@51478
   660
lemma continuous_power [continuous_intros]:
hoelzl@51478
   661
  fixes f :: "'a::t2_space \<Rightarrow> 'b::{power,real_normed_algebra}"
hoelzl@51478
   662
  shows "continuous F f \<Longrightarrow> continuous F (\<lambda>x. (f x)^n)"
hoelzl@51478
   663
  unfolding continuous_def by (rule tendsto_power)
hoelzl@51478
   664
hoelzl@51478
   665
lemma continuous_on_power [continuous_on_intros]:
hoelzl@51478
   666
  fixes f :: "_ \<Rightarrow> 'b::{power,real_normed_algebra}"
hoelzl@51478
   667
  shows "continuous_on s f \<Longrightarrow> continuous_on s (\<lambda>x. (f x)^n)"
hoelzl@51478
   668
  unfolding continuous_on_def by (auto intro: tendsto_power)
hoelzl@51478
   669
huffman@44194
   670
lemma tendsto_setprod [tendsto_intros]:
huffman@44194
   671
  fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'c::{real_normed_algebra,comm_ring_1}"
huffman@44195
   672
  assumes "\<And>i. i \<in> S \<Longrightarrow> (f i ---> L i) F"
huffman@44195
   673
  shows "((\<lambda>x. \<Prod>i\<in>S. f i x) ---> (\<Prod>i\<in>S. L i)) F"
huffman@44194
   674
proof (cases "finite S")
huffman@44194
   675
  assume "finite S" thus ?thesis using assms
huffman@44194
   676
    by (induct, simp add: tendsto_const, simp add: tendsto_mult)
huffman@44194
   677
next
huffman@44194
   678
  assume "\<not> finite S" thus ?thesis
huffman@44194
   679
    by (simp add: tendsto_const)
huffman@44194
   680
qed
huffman@44194
   681
hoelzl@51478
   682
lemma continuous_setprod [continuous_intros]:
hoelzl@51478
   683
  fixes f :: "'a \<Rightarrow> 'b::t2_space \<Rightarrow> 'c::{real_normed_algebra,comm_ring_1}"
hoelzl@51478
   684
  shows "(\<And>i. i \<in> S \<Longrightarrow> continuous F (f i)) \<Longrightarrow> continuous F (\<lambda>x. \<Prod>i\<in>S. f i x)"
hoelzl@51478
   685
  unfolding continuous_def by (rule tendsto_setprod)
hoelzl@51478
   686
hoelzl@51478
   687
lemma continuous_on_setprod [continuous_intros]:
hoelzl@51478
   688
  fixes f :: "'a \<Rightarrow> _ \<Rightarrow> 'c::{real_normed_algebra,comm_ring_1}"
hoelzl@51478
   689
  shows "(\<And>i. i \<in> S \<Longrightarrow> continuous_on s (f i)) \<Longrightarrow> continuous_on s (\<lambda>x. \<Prod>i\<in>S. f i x)"
hoelzl@51478
   690
  unfolding continuous_on_def by (auto intro: tendsto_setprod)
hoelzl@51478
   691
huffman@44194
   692
subsubsection {* Inverse and division *}
huffman@31355
   693
huffman@31355
   694
lemma (in bounded_bilinear) Zfun_prod_Bfun:
huffman@44195
   695
  assumes f: "Zfun f F"
huffman@44195
   696
  assumes g: "Bfun g F"
huffman@44195
   697
  shows "Zfun (\<lambda>x. f x ** g x) F"
huffman@31355
   698
proof -
huffman@31355
   699
  obtain K where K: "0 \<le> K"
huffman@31355
   700
    and norm_le: "\<And>x y. norm (x ** y) \<le> norm x * norm y * K"
huffman@31355
   701
    using nonneg_bounded by fast
huffman@31355
   702
  obtain B where B: "0 < B"
huffman@44195
   703
    and norm_g: "eventually (\<lambda>x. norm (g x) \<le> B) F"
huffman@31487
   704
    using g by (rule BfunE)
huffman@44195
   705
  have "eventually (\<lambda>x. norm (f x ** g x) \<le> norm (f x) * (B * K)) F"
noschinl@46887
   706
  using norm_g proof eventually_elim
noschinl@46887
   707
    case (elim x)
huffman@31487
   708
    have "norm (f x ** g x) \<le> norm (f x) * norm (g x) * K"
huffman@31355
   709
      by (rule norm_le)
huffman@31487
   710
    also have "\<dots> \<le> norm (f x) * B * K"
huffman@31487
   711
      by (intro mult_mono' order_refl norm_g norm_ge_zero
noschinl@46887
   712
                mult_nonneg_nonneg K elim)
huffman@31487
   713
    also have "\<dots> = norm (f x) * (B * K)"
huffman@31355
   714
      by (rule mult_assoc)
huffman@31487
   715
    finally show "norm (f x ** g x) \<le> norm (f x) * (B * K)" .
huffman@31355
   716
  qed
huffman@31487
   717
  with f show ?thesis
huffman@31487
   718
    by (rule Zfun_imp_Zfun)
huffman@31355
   719
qed
huffman@31355
   720
huffman@31355
   721
lemma (in bounded_bilinear) flip:
huffman@31355
   722
  "bounded_bilinear (\<lambda>x y. y ** x)"
huffman@44081
   723
  apply default
huffman@44081
   724
  apply (rule add_right)
huffman@44081
   725
  apply (rule add_left)
huffman@44081
   726
  apply (rule scaleR_right)
huffman@44081
   727
  apply (rule scaleR_left)
huffman@44081
   728
  apply (subst mult_commute)
huffman@44081
   729
  using bounded by fast
huffman@31355
   730
huffman@31355
   731
lemma (in bounded_bilinear) Bfun_prod_Zfun:
huffman@44195
   732
  assumes f: "Bfun f F"
huffman@44195
   733
  assumes g: "Zfun g F"
huffman@44195
   734
  shows "Zfun (\<lambda>x. f x ** g x) F"
huffman@44081
   735
  using flip g f by (rule bounded_bilinear.Zfun_prod_Bfun)
huffman@31355
   736
huffman@31355
   737
lemma Bfun_inverse_lemma:
huffman@31355
   738
  fixes x :: "'a::real_normed_div_algebra"
huffman@31355
   739
  shows "\<lbrakk>r \<le> norm x; 0 < r\<rbrakk> \<Longrightarrow> norm (inverse x) \<le> inverse r"
huffman@44081
   740
  apply (subst nonzero_norm_inverse, clarsimp)
huffman@44081
   741
  apply (erule (1) le_imp_inverse_le)
huffman@44081
   742
  done
huffman@31355
   743
huffman@31355
   744
lemma Bfun_inverse:
huffman@31355
   745
  fixes a :: "'a::real_normed_div_algebra"
huffman@44195
   746
  assumes f: "(f ---> a) F"
huffman@31355
   747
  assumes a: "a \<noteq> 0"
huffman@44195
   748
  shows "Bfun (\<lambda>x. inverse (f x)) F"
huffman@31355
   749
proof -
huffman@31355
   750
  from a have "0 < norm a" by simp
huffman@31355
   751
  hence "\<exists>r>0. r < norm a" by (rule dense)
huffman@31355
   752
  then obtain r where r1: "0 < r" and r2: "r < norm a" by fast
huffman@44195
   753
  have "eventually (\<lambda>x. dist (f x) a < r) F"
huffman@31487
   754
    using tendstoD [OF f r1] by fast
huffman@44195
   755
  hence "eventually (\<lambda>x. norm (inverse (f x)) \<le> inverse (norm a - r)) F"
noschinl@46887
   756
  proof eventually_elim
noschinl@46887
   757
    case (elim x)
huffman@31487
   758
    hence 1: "norm (f x - a) < r"
huffman@31355
   759
      by (simp add: dist_norm)
huffman@31487
   760
    hence 2: "f x \<noteq> 0" using r2 by auto
huffman@31487
   761
    hence "norm (inverse (f x)) = inverse (norm (f x))"
huffman@31355
   762
      by (rule nonzero_norm_inverse)
huffman@31355
   763
    also have "\<dots> \<le> inverse (norm a - r)"
huffman@31355
   764
    proof (rule le_imp_inverse_le)
huffman@31355
   765
      show "0 < norm a - r" using r2 by simp
huffman@31355
   766
    next
huffman@31487
   767
      have "norm a - norm (f x) \<le> norm (a - f x)"
huffman@31355
   768
        by (rule norm_triangle_ineq2)
huffman@31487
   769
      also have "\<dots> = norm (f x - a)"
huffman@31355
   770
        by (rule norm_minus_commute)
huffman@31355
   771
      also have "\<dots> < r" using 1 .
huffman@31487
   772
      finally show "norm a - r \<le> norm (f x)" by simp
huffman@31355
   773
    qed
huffman@31487
   774
    finally show "norm (inverse (f x)) \<le> inverse (norm a - r)" .
huffman@31355
   775
  qed
huffman@31355
   776
  thus ?thesis by (rule BfunI)
huffman@31355
   777
qed
huffman@31355
   778
huffman@31565
   779
lemma tendsto_inverse [tendsto_intros]:
huffman@31355
   780
  fixes a :: "'a::real_normed_div_algebra"
huffman@44195
   781
  assumes f: "(f ---> a) F"
huffman@31355
   782
  assumes a: "a \<noteq> 0"
huffman@44195
   783
  shows "((\<lambda>x. inverse (f x)) ---> inverse a) F"
huffman@31355
   784
proof -
huffman@31355
   785
  from a have "0 < norm a" by simp
huffman@44195
   786
  with f have "eventually (\<lambda>x. dist (f x) a < norm a) F"
huffman@31355
   787
    by (rule tendstoD)
huffman@44195
   788
  then have "eventually (\<lambda>x. f x \<noteq> 0) F"
huffman@31355
   789
    unfolding dist_norm by (auto elim!: eventually_elim1)
huffman@44627
   790
  with a have "eventually (\<lambda>x. inverse (f x) - inverse a =
huffman@44627
   791
    - (inverse (f x) * (f x - a) * inverse a)) F"
huffman@44627
   792
    by (auto elim!: eventually_elim1 simp: inverse_diff_inverse)
huffman@44627
   793
  moreover have "Zfun (\<lambda>x. - (inverse (f x) * (f x - a) * inverse a)) F"
huffman@44627
   794
    by (intro Zfun_minus Zfun_mult_left
huffman@44627
   795
      bounded_bilinear.Bfun_prod_Zfun [OF bounded_bilinear_mult]
huffman@44627
   796
      Bfun_inverse [OF f a] f [unfolded tendsto_Zfun_iff])
huffman@44627
   797
  ultimately show ?thesis
huffman@44627
   798
    unfolding tendsto_Zfun_iff by (rule Zfun_ssubst)
huffman@31355
   799
qed
huffman@31355
   800
hoelzl@51478
   801
lemma continuous_inverse:
hoelzl@51478
   802
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_div_algebra"
hoelzl@51478
   803
  assumes "continuous F f" and "f (Lim F (\<lambda>x. x)) \<noteq> 0"
hoelzl@51478
   804
  shows "continuous F (\<lambda>x. inverse (f x))"
hoelzl@51478
   805
  using assms unfolding continuous_def by (rule tendsto_inverse)
hoelzl@51478
   806
hoelzl@51478
   807
lemma continuous_at_within_inverse[continuous_intros]:
hoelzl@51478
   808
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_div_algebra"
hoelzl@51478
   809
  assumes "continuous (at a within s) f" and "f a \<noteq> 0"
hoelzl@51478
   810
  shows "continuous (at a within s) (\<lambda>x. inverse (f x))"
hoelzl@51478
   811
  using assms unfolding continuous_within by (rule tendsto_inverse)
hoelzl@51478
   812
hoelzl@51478
   813
lemma isCont_inverse[continuous_intros, simp]:
hoelzl@51478
   814
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_div_algebra"
hoelzl@51478
   815
  assumes "isCont f a" and "f a \<noteq> 0"
hoelzl@51478
   816
  shows "isCont (\<lambda>x. inverse (f x)) a"
hoelzl@51478
   817
  using assms unfolding continuous_at by (rule tendsto_inverse)
hoelzl@51478
   818
hoelzl@51478
   819
lemma continuous_on_inverse[continuous_on_intros]:
hoelzl@51478
   820
  fixes f :: "'a::topological_space \<Rightarrow> 'b::real_normed_div_algebra"
hoelzl@51478
   821
  assumes "continuous_on s f" and "\<forall>x\<in>s. f x \<noteq> 0"
hoelzl@51478
   822
  shows "continuous_on s (\<lambda>x. inverse (f x))"
hoelzl@51478
   823
  using assms unfolding continuous_on_def by (fast intro: tendsto_inverse)
hoelzl@51478
   824
huffman@31565
   825
lemma tendsto_divide [tendsto_intros]:
huffman@31355
   826
  fixes a b :: "'a::real_normed_field"
huffman@44195
   827
  shows "\<lbrakk>(f ---> a) F; (g ---> b) F; b \<noteq> 0\<rbrakk>
huffman@44195
   828
    \<Longrightarrow> ((\<lambda>x. f x / g x) ---> a / b) F"
huffman@44282
   829
  by (simp add: tendsto_mult tendsto_inverse divide_inverse)
huffman@31355
   830
hoelzl@51478
   831
lemma continuous_divide:
hoelzl@51478
   832
  fixes f g :: "'a::t2_space \<Rightarrow> 'b::real_normed_field"
hoelzl@51478
   833
  assumes "continuous F f" and "continuous F g" and "g (Lim F (\<lambda>x. x)) \<noteq> 0"
hoelzl@51478
   834
  shows "continuous F (\<lambda>x. (f x) / (g x))"
hoelzl@51478
   835
  using assms unfolding continuous_def by (rule tendsto_divide)
hoelzl@51478
   836
hoelzl@51478
   837
lemma continuous_at_within_divide[continuous_intros]:
hoelzl@51478
   838
  fixes f g :: "'a::t2_space \<Rightarrow> 'b::real_normed_field"
hoelzl@51478
   839
  assumes "continuous (at a within s) f" "continuous (at a within s) g" and "g a \<noteq> 0"
hoelzl@51478
   840
  shows "continuous (at a within s) (\<lambda>x. (f x) / (g x))"
hoelzl@51478
   841
  using assms unfolding continuous_within by (rule tendsto_divide)
hoelzl@51478
   842
hoelzl@51478
   843
lemma isCont_divide[continuous_intros, simp]:
hoelzl@51478
   844
  fixes f g :: "'a::t2_space \<Rightarrow> 'b::real_normed_field"
hoelzl@51478
   845
  assumes "isCont f a" "isCont g a" "g a \<noteq> 0"
hoelzl@51478
   846
  shows "isCont (\<lambda>x. (f x) / g x) a"
hoelzl@51478
   847
  using assms unfolding continuous_at by (rule tendsto_divide)
hoelzl@51478
   848
hoelzl@51478
   849
lemma continuous_on_divide[continuous_on_intros]:
hoelzl@51478
   850
  fixes f :: "'a::topological_space \<Rightarrow> 'b::real_normed_field"
hoelzl@51478
   851
  assumes "continuous_on s f" "continuous_on s g" and "\<forall>x\<in>s. g x \<noteq> 0"
hoelzl@51478
   852
  shows "continuous_on s (\<lambda>x. (f x) / (g x))"
hoelzl@51478
   853
  using assms unfolding continuous_on_def by (fast intro: tendsto_divide)
hoelzl@51478
   854
huffman@44194
   855
lemma tendsto_sgn [tendsto_intros]:
huffman@44194
   856
  fixes l :: "'a::real_normed_vector"
huffman@44195
   857
  shows "\<lbrakk>(f ---> l) F; l \<noteq> 0\<rbrakk> \<Longrightarrow> ((\<lambda>x. sgn (f x)) ---> sgn l) F"
huffman@44194
   858
  unfolding sgn_div_norm by (simp add: tendsto_intros)
huffman@44194
   859
hoelzl@51478
   860
lemma continuous_sgn:
hoelzl@51478
   861
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   862
  assumes "continuous F f" and "f (Lim F (\<lambda>x. x)) \<noteq> 0"
hoelzl@51478
   863
  shows "continuous F (\<lambda>x. sgn (f x))"
hoelzl@51478
   864
  using assms unfolding continuous_def by (rule tendsto_sgn)
hoelzl@51478
   865
hoelzl@51478
   866
lemma continuous_at_within_sgn[continuous_intros]:
hoelzl@51478
   867
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   868
  assumes "continuous (at a within s) f" and "f a \<noteq> 0"
hoelzl@51478
   869
  shows "continuous (at a within s) (\<lambda>x. sgn (f x))"
hoelzl@51478
   870
  using assms unfolding continuous_within by (rule tendsto_sgn)
hoelzl@51478
   871
hoelzl@51478
   872
lemma isCont_sgn[continuous_intros]:
hoelzl@51478
   873
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   874
  assumes "isCont f a" and "f a \<noteq> 0"
hoelzl@51478
   875
  shows "isCont (\<lambda>x. sgn (f x)) a"
hoelzl@51478
   876
  using assms unfolding continuous_at by (rule tendsto_sgn)
hoelzl@51478
   877
hoelzl@51478
   878
lemma continuous_on_sgn[continuous_on_intros]:
hoelzl@51478
   879
  fixes f :: "'a::topological_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51478
   880
  assumes "continuous_on s f" and "\<forall>x\<in>s. f x \<noteq> 0"
hoelzl@51478
   881
  shows "continuous_on s (\<lambda>x. sgn (f x))"
hoelzl@51478
   882
  using assms unfolding continuous_on_def by (fast intro: tendsto_sgn)
hoelzl@51478
   883
hoelzl@50325
   884
lemma filterlim_at_infinity:
hoelzl@50325
   885
  fixes f :: "_ \<Rightarrow> 'a\<Colon>real_normed_vector"
hoelzl@50325
   886
  assumes "0 \<le> c"
hoelzl@50325
   887
  shows "(LIM x F. f x :> at_infinity) \<longleftrightarrow> (\<forall>r>c. eventually (\<lambda>x. r \<le> norm (f x)) F)"
hoelzl@50325
   888
  unfolding filterlim_iff eventually_at_infinity
hoelzl@50325
   889
proof safe
hoelzl@50325
   890
  fix P :: "'a \<Rightarrow> bool" and b
hoelzl@50325
   891
  assume *: "\<forall>r>c. eventually (\<lambda>x. r \<le> norm (f x)) F"
hoelzl@50325
   892
    and P: "\<forall>x. b \<le> norm x \<longrightarrow> P x"
hoelzl@50325
   893
  have "max b (c + 1) > c" by auto
hoelzl@50325
   894
  with * have "eventually (\<lambda>x. max b (c + 1) \<le> norm (f x)) F"
hoelzl@50325
   895
    by auto
hoelzl@50325
   896
  then show "eventually (\<lambda>x. P (f x)) F"
hoelzl@50325
   897
  proof eventually_elim
hoelzl@50325
   898
    fix x assume "max b (c + 1) \<le> norm (f x)"
hoelzl@50325
   899
    with P show "P (f x)" by auto
hoelzl@50325
   900
  qed
hoelzl@50325
   901
qed force
hoelzl@50325
   902
hoelzl@51529
   903
hoelzl@50347
   904
subsection {* Relate @{const at}, @{const at_left} and @{const at_right} *}
hoelzl@50347
   905
hoelzl@50347
   906
text {*
hoelzl@50347
   907
hoelzl@50347
   908
This lemmas are useful for conversion between @{term "at x"} to @{term "at_left x"} and
hoelzl@50347
   909
@{term "at_right x"} and also @{term "at_right 0"}.
hoelzl@50347
   910
hoelzl@50347
   911
*}
hoelzl@50347
   912
hoelzl@51471
   913
lemmas filterlim_split_at_real = filterlim_split_at[where 'a=real]
hoelzl@50323
   914
hoelzl@51641
   915
lemma filtermap_homeomorph:
hoelzl@51641
   916
  assumes f: "continuous (at a) f"
hoelzl@51641
   917
  assumes g: "continuous (at (f a)) g"
hoelzl@51641
   918
  assumes bij1: "\<forall>x. f (g x) = x" and bij2: "\<forall>x. g (f x) = x"
hoelzl@51641
   919
  shows "filtermap f (nhds a) = nhds (f a)"
hoelzl@51641
   920
  unfolding filter_eq_iff eventually_filtermap eventually_nhds
hoelzl@51641
   921
proof safe
hoelzl@51641
   922
  fix P S assume S: "open S" "f a \<in> S" and P: "\<forall>x\<in>S. P x"
hoelzl@51641
   923
  from continuous_within_topological[THEN iffD1, rule_format, OF f S] P
hoelzl@51641
   924
  show "\<exists>S. open S \<and> a \<in> S \<and> (\<forall>x\<in>S. P (f x))" by auto
hoelzl@51641
   925
next
hoelzl@51641
   926
  fix P S assume S: "open S" "a \<in> S" and P: "\<forall>x\<in>S. P (f x)"
hoelzl@51641
   927
  with continuous_within_topological[THEN iffD1, rule_format, OF g, of S] bij2
hoelzl@51641
   928
  obtain A where "open A" "f a \<in> A" "(\<forall>y\<in>A. g y \<in> S)"
hoelzl@51641
   929
    by (metis UNIV_I)
hoelzl@51641
   930
  with P bij1 show "\<exists>S. open S \<and> f a \<in> S \<and> (\<forall>x\<in>S. P x)"
hoelzl@51641
   931
    by (force intro!: exI[of _ A])
hoelzl@51641
   932
qed
hoelzl@50347
   933
hoelzl@51641
   934
lemma filtermap_nhds_shift: "filtermap (\<lambda>x. x - d) (nhds a) = nhds (a - d::'a::real_normed_vector)"
hoelzl@51641
   935
  by (rule filtermap_homeomorph[where g="\<lambda>x. x + d"]) (auto intro: continuous_intros)
hoelzl@50347
   936
hoelzl@51641
   937
lemma filtermap_nhds_minus: "filtermap (\<lambda>x. - x) (nhds a) = nhds (- a::'a::real_normed_vector)"
hoelzl@51641
   938
  by (rule filtermap_homeomorph[where g=uminus]) (auto intro: continuous_minus)
hoelzl@51641
   939
hoelzl@51641
   940
lemma filtermap_at_shift: "filtermap (\<lambda>x. x - d) (at a) = at (a - d::'a::real_normed_vector)"
hoelzl@51641
   941
  by (simp add: filter_eq_iff eventually_filtermap eventually_at_filter filtermap_nhds_shift[symmetric])
hoelzl@50347
   942
hoelzl@50347
   943
lemma filtermap_at_right_shift: "filtermap (\<lambda>x. x - d) (at_right a) = at_right (a - d::real)"
hoelzl@51641
   944
  by (simp add: filter_eq_iff eventually_filtermap eventually_at_filter filtermap_nhds_shift[symmetric])
hoelzl@50323
   945
hoelzl@50347
   946
lemma at_right_to_0: "at_right (a::real) = filtermap (\<lambda>x. x + a) (at_right 0)"
hoelzl@50347
   947
  using filtermap_at_right_shift[of "-a" 0] by simp
hoelzl@50347
   948
hoelzl@50347
   949
lemma filterlim_at_right_to_0:
hoelzl@50347
   950
  "filterlim f F (at_right (a::real)) \<longleftrightarrow> filterlim (\<lambda>x. f (x + a)) F (at_right 0)"
hoelzl@50347
   951
  unfolding filterlim_def filtermap_filtermap at_right_to_0[of a] ..
hoelzl@50347
   952
hoelzl@50347
   953
lemma eventually_at_right_to_0:
hoelzl@50347
   954
  "eventually P (at_right (a::real)) \<longleftrightarrow> eventually (\<lambda>x. P (x + a)) (at_right 0)"
hoelzl@50347
   955
  unfolding at_right_to_0[of a] by (simp add: eventually_filtermap)
hoelzl@50347
   956
hoelzl@51641
   957
lemma filtermap_at_minus: "filtermap (\<lambda>x. - x) (at a) = at (- a::'a::real_normed_vector)"
hoelzl@51641
   958
  by (simp add: filter_eq_iff eventually_filtermap eventually_at_filter filtermap_nhds_minus[symmetric])
hoelzl@50347
   959
hoelzl@50347
   960
lemma at_left_minus: "at_left (a::real) = filtermap (\<lambda>x. - x) (at_right (- a))"
hoelzl@51641
   961
  by (simp add: filter_eq_iff eventually_filtermap eventually_at_filter filtermap_nhds_minus[symmetric])
hoelzl@50323
   962
hoelzl@50347
   963
lemma at_right_minus: "at_right (a::real) = filtermap (\<lambda>x. - x) (at_left (- a))"
hoelzl@51641
   964
  by (simp add: filter_eq_iff eventually_filtermap eventually_at_filter filtermap_nhds_minus[symmetric])
hoelzl@50347
   965
hoelzl@50347
   966
lemma filterlim_at_left_to_right:
hoelzl@50347
   967
  "filterlim f F (at_left (a::real)) \<longleftrightarrow> filterlim (\<lambda>x. f (- x)) F (at_right (-a))"
hoelzl@50347
   968
  unfolding filterlim_def filtermap_filtermap at_left_minus[of a] ..
hoelzl@50347
   969
hoelzl@50347
   970
lemma eventually_at_left_to_right:
hoelzl@50347
   971
  "eventually P (at_left (a::real)) \<longleftrightarrow> eventually (\<lambda>x. P (- x)) (at_right (-a))"
hoelzl@50347
   972
  unfolding at_left_minus[of a] by (simp add: eventually_filtermap)
hoelzl@50347
   973
hoelzl@50346
   974
lemma at_top_mirror: "at_top = filtermap uminus (at_bot :: real filter)"
hoelzl@50346
   975
  unfolding filter_eq_iff eventually_filtermap eventually_at_top_linorder eventually_at_bot_linorder
hoelzl@50346
   976
  by (metis le_minus_iff minus_minus)
hoelzl@50346
   977
hoelzl@50346
   978
lemma at_bot_mirror: "at_bot = filtermap uminus (at_top :: real filter)"
hoelzl@50346
   979
  unfolding at_top_mirror filtermap_filtermap by (simp add: filtermap_ident)
hoelzl@50346
   980
hoelzl@50346
   981
lemma filterlim_at_top_mirror: "(LIM x at_top. f x :> F) \<longleftrightarrow> (LIM x at_bot. f (-x::real) :> F)"
hoelzl@50346
   982
  unfolding filterlim_def at_top_mirror filtermap_filtermap ..
hoelzl@50346
   983
hoelzl@50346
   984
lemma filterlim_at_bot_mirror: "(LIM x at_bot. f x :> F) \<longleftrightarrow> (LIM x at_top. f (-x::real) :> F)"
hoelzl@50346
   985
  unfolding filterlim_def at_bot_mirror filtermap_filtermap ..
hoelzl@50346
   986
hoelzl@50323
   987
lemma filterlim_uminus_at_top_at_bot: "LIM x at_bot. - x :: real :> at_top"
hoelzl@50323
   988
  unfolding filterlim_at_top eventually_at_bot_dense
hoelzl@50346
   989
  by (metis leI minus_less_iff order_less_asym)
hoelzl@50323
   990
hoelzl@50323
   991
lemma filterlim_uminus_at_bot_at_top: "LIM x at_top. - x :: real :> at_bot"
hoelzl@50323
   992
  unfolding filterlim_at_bot eventually_at_top_dense
hoelzl@50346
   993
  by (metis leI less_minus_iff order_less_asym)
hoelzl@50323
   994
hoelzl@50346
   995
lemma filterlim_uminus_at_top: "(LIM x F. f x :> at_top) \<longleftrightarrow> (LIM x F. - (f x) :: real :> at_bot)"
hoelzl@50346
   996
  using filterlim_compose[OF filterlim_uminus_at_bot_at_top, of f F]
hoelzl@50346
   997
  using filterlim_compose[OF filterlim_uminus_at_top_at_bot, of "\<lambda>x. - f x" F]
hoelzl@50346
   998
  by auto
hoelzl@50346
   999
hoelzl@50346
  1000
lemma filterlim_uminus_at_bot: "(LIM x F. f x :> at_bot) \<longleftrightarrow> (LIM x F. - (f x) :: real :> at_top)"
hoelzl@50346
  1001
  unfolding filterlim_uminus_at_top by simp
hoelzl@50323
  1002
hoelzl@50347
  1003
lemma filterlim_inverse_at_top_right: "LIM x at_right (0::real). inverse x :> at_top"
hoelzl@51641
  1004
  unfolding filterlim_at_top_gt[where c=0] eventually_at_filter
hoelzl@50347
  1005
proof safe
hoelzl@50347
  1006
  fix Z :: real assume [arith]: "0 < Z"
hoelzl@50347
  1007
  then have "eventually (\<lambda>x. x < inverse Z) (nhds 0)"
hoelzl@50347
  1008
    by (auto simp add: eventually_nhds_metric dist_real_def intro!: exI[of _ "\<bar>inverse Z\<bar>"])
hoelzl@51641
  1009
  then show "eventually (\<lambda>x. x \<noteq> 0 \<longrightarrow> x \<in> {0<..} \<longrightarrow> Z \<le> inverse x) (nhds 0)"
hoelzl@50347
  1010
    by (auto elim!: eventually_elim1 simp: inverse_eq_divide field_simps)
hoelzl@50347
  1011
qed
hoelzl@50347
  1012
hoelzl@50347
  1013
lemma filterlim_inverse_at_top:
hoelzl@50347
  1014
  "(f ---> (0 :: real)) F \<Longrightarrow> eventually (\<lambda>x. 0 < f x) F \<Longrightarrow> LIM x F. inverse (f x) :> at_top"
hoelzl@50347
  1015
  by (intro filterlim_compose[OF filterlim_inverse_at_top_right])
hoelzl@51641
  1016
     (simp add: filterlim_def eventually_filtermap eventually_elim1 at_within_def le_principal)
hoelzl@50347
  1017
hoelzl@50347
  1018
lemma filterlim_inverse_at_bot_neg:
hoelzl@50347
  1019
  "LIM x (at_left (0::real)). inverse x :> at_bot"
hoelzl@50347
  1020
  by (simp add: filterlim_inverse_at_top_right filterlim_uminus_at_bot filterlim_at_left_to_right)
hoelzl@50347
  1021
hoelzl@50347
  1022
lemma filterlim_inverse_at_bot:
hoelzl@50347
  1023
  "(f ---> (0 :: real)) F \<Longrightarrow> eventually (\<lambda>x. f x < 0) F \<Longrightarrow> LIM x F. inverse (f x) :> at_bot"
hoelzl@50347
  1024
  unfolding filterlim_uminus_at_bot inverse_minus_eq[symmetric]
hoelzl@50347
  1025
  by (rule filterlim_inverse_at_top) (simp_all add: tendsto_minus_cancel_left[symmetric])
hoelzl@50347
  1026
hoelzl@50325
  1027
lemma tendsto_inverse_0:
hoelzl@50325
  1028
  fixes x :: "_ \<Rightarrow> 'a\<Colon>real_normed_div_algebra"
hoelzl@50325
  1029
  shows "(inverse ---> (0::'a)) at_infinity"
hoelzl@50325
  1030
  unfolding tendsto_Zfun_iff diff_0_right Zfun_def eventually_at_infinity
hoelzl@50325
  1031
proof safe
hoelzl@50325
  1032
  fix r :: real assume "0 < r"
hoelzl@50325
  1033
  show "\<exists>b. \<forall>x. b \<le> norm x \<longrightarrow> norm (inverse x :: 'a) < r"
hoelzl@50325
  1034
  proof (intro exI[of _ "inverse (r / 2)"] allI impI)
hoelzl@50325
  1035
    fix x :: 'a
hoelzl@50325
  1036
    from `0 < r` have "0 < inverse (r / 2)" by simp
hoelzl@50325
  1037
    also assume *: "inverse (r / 2) \<le> norm x"
hoelzl@50325
  1038
    finally show "norm (inverse x) < r"
hoelzl@50325
  1039
      using * `0 < r` by (subst nonzero_norm_inverse) (simp_all add: inverse_eq_divide field_simps)
hoelzl@50325
  1040
  qed
hoelzl@50325
  1041
qed
hoelzl@50325
  1042
hoelzl@50347
  1043
lemma at_right_to_top: "(at_right (0::real)) = filtermap inverse at_top"
hoelzl@50347
  1044
proof (rule antisym)
hoelzl@50347
  1045
  have "(inverse ---> (0::real)) at_top"
hoelzl@50347
  1046
    by (metis tendsto_inverse_0 filterlim_mono at_top_le_at_infinity order_refl)
hoelzl@50347
  1047
  then show "filtermap inverse at_top \<le> at_right (0::real)"
hoelzl@51641
  1048
    by (simp add: le_principal eventually_filtermap eventually_gt_at_top filterlim_def at_within_def)
hoelzl@50347
  1049
next
hoelzl@50347
  1050
  have "filtermap inverse (filtermap inverse (at_right (0::real))) \<le> filtermap inverse at_top"
hoelzl@50347
  1051
    using filterlim_inverse_at_top_right unfolding filterlim_def by (rule filtermap_mono)
hoelzl@50347
  1052
  then show "at_right (0::real) \<le> filtermap inverse at_top"
hoelzl@50347
  1053
    by (simp add: filtermap_ident filtermap_filtermap)
hoelzl@50347
  1054
qed
hoelzl@50347
  1055
hoelzl@50347
  1056
lemma eventually_at_right_to_top:
hoelzl@50347
  1057
  "eventually P (at_right (0::real)) \<longleftrightarrow> eventually (\<lambda>x. P (inverse x)) at_top"
hoelzl@50347
  1058
  unfolding at_right_to_top eventually_filtermap ..
hoelzl@50347
  1059
hoelzl@50347
  1060
lemma filterlim_at_right_to_top:
hoelzl@50347
  1061
  "filterlim f F (at_right (0::real)) \<longleftrightarrow> (LIM x at_top. f (inverse x) :> F)"
hoelzl@50347
  1062
  unfolding filterlim_def at_right_to_top filtermap_filtermap ..
hoelzl@50347
  1063
hoelzl@50347
  1064
lemma at_top_to_right: "at_top = filtermap inverse (at_right (0::real))"
hoelzl@50347
  1065
  unfolding at_right_to_top filtermap_filtermap inverse_inverse_eq filtermap_ident ..
hoelzl@50347
  1066
hoelzl@50347
  1067
lemma eventually_at_top_to_right:
hoelzl@50347
  1068
  "eventually P at_top \<longleftrightarrow> eventually (\<lambda>x. P (inverse x)) (at_right (0::real))"
hoelzl@50347
  1069
  unfolding at_top_to_right eventually_filtermap ..
hoelzl@50347
  1070
hoelzl@50347
  1071
lemma filterlim_at_top_to_right:
hoelzl@50347
  1072
  "filterlim f F at_top \<longleftrightarrow> (LIM x (at_right (0::real)). f (inverse x) :> F)"
hoelzl@50347
  1073
  unfolding filterlim_def at_top_to_right filtermap_filtermap ..
hoelzl@50347
  1074
hoelzl@50325
  1075
lemma filterlim_inverse_at_infinity:
hoelzl@50325
  1076
  fixes x :: "_ \<Rightarrow> 'a\<Colon>{real_normed_div_algebra, division_ring_inverse_zero}"
hoelzl@50325
  1077
  shows "filterlim inverse at_infinity (at (0::'a))"
hoelzl@50325
  1078
  unfolding filterlim_at_infinity[OF order_refl]
hoelzl@50325
  1079
proof safe
hoelzl@50325
  1080
  fix r :: real assume "0 < r"
hoelzl@50325
  1081
  then show "eventually (\<lambda>x::'a. r \<le> norm (inverse x)) (at 0)"
hoelzl@50325
  1082
    unfolding eventually_at norm_inverse
hoelzl@50325
  1083
    by (intro exI[of _ "inverse r"])
hoelzl@50325
  1084
       (auto simp: norm_conv_dist[symmetric] field_simps inverse_eq_divide)
hoelzl@50325
  1085
qed
hoelzl@50325
  1086
hoelzl@50325
  1087
lemma filterlim_inverse_at_iff:
hoelzl@50325
  1088
  fixes g :: "'a \<Rightarrow> 'b\<Colon>{real_normed_div_algebra, division_ring_inverse_zero}"
hoelzl@50325
  1089
  shows "(LIM x F. inverse (g x) :> at 0) \<longleftrightarrow> (LIM x F. g x :> at_infinity)"
hoelzl@50325
  1090
  unfolding filterlim_def filtermap_filtermap[symmetric]
hoelzl@50325
  1091
proof
hoelzl@50325
  1092
  assume "filtermap g F \<le> at_infinity"
hoelzl@50325
  1093
  then have "filtermap inverse (filtermap g F) \<le> filtermap inverse at_infinity"
hoelzl@50325
  1094
    by (rule filtermap_mono)
hoelzl@50325
  1095
  also have "\<dots> \<le> at 0"
hoelzl@51641
  1096
    using tendsto_inverse_0[where 'a='b]
hoelzl@51641
  1097
    by (auto intro!: exI[of _ 1]
hoelzl@51641
  1098
             simp: le_principal eventually_filtermap filterlim_def at_within_def eventually_at_infinity)
hoelzl@50325
  1099
  finally show "filtermap inverse (filtermap g F) \<le> at 0" .
hoelzl@50325
  1100
next
hoelzl@50325
  1101
  assume "filtermap inverse (filtermap g F) \<le> at 0"
hoelzl@50325
  1102
  then have "filtermap inverse (filtermap inverse (filtermap g F)) \<le> filtermap inverse (at 0)"
hoelzl@50325
  1103
    by (rule filtermap_mono)
hoelzl@50325
  1104
  with filterlim_inverse_at_infinity show "filtermap g F \<le> at_infinity"
hoelzl@50325
  1105
    by (auto intro: order_trans simp: filterlim_def filtermap_filtermap)
hoelzl@50325
  1106
qed
hoelzl@50325
  1107
hoelzl@51641
  1108
lemma tendsto_inverse_0_at_top: "LIM x F. f x :> at_top \<Longrightarrow> ((\<lambda>x. inverse (f x) :: real) ---> 0) F"
hoelzl@51641
  1109
 by (metis filterlim_at filterlim_mono[OF _ at_top_le_at_infinity order_refl] filterlim_inverse_at_iff)
hoelzl@50419
  1110
hoelzl@50324
  1111
text {*
hoelzl@50324
  1112
hoelzl@50324
  1113
We only show rules for multiplication and addition when the functions are either against a real
hoelzl@50324
  1114
value or against infinity. Further rules are easy to derive by using @{thm filterlim_uminus_at_top}.
hoelzl@50324
  1115
hoelzl@50324
  1116
*}
hoelzl@50324
  1117
hoelzl@50324
  1118
lemma filterlim_tendsto_pos_mult_at_top: 
hoelzl@50324
  1119
  assumes f: "(f ---> c) F" and c: "0 < c"
hoelzl@50324
  1120
  assumes g: "LIM x F. g x :> at_top"
hoelzl@50324
  1121
  shows "LIM x F. (f x * g x :: real) :> at_top"
hoelzl@50324
  1122
  unfolding filterlim_at_top_gt[where c=0]
hoelzl@50324
  1123
proof safe
hoelzl@50324
  1124
  fix Z :: real assume "0 < Z"
hoelzl@50324
  1125
  from f `0 < c` have "eventually (\<lambda>x. c / 2 < f x) F"
hoelzl@50324
  1126
    by (auto dest!: tendstoD[where e="c / 2"] elim!: eventually_elim1
hoelzl@50324
  1127
             simp: dist_real_def abs_real_def split: split_if_asm)
hoelzl@50346
  1128
  moreover from g have "eventually (\<lambda>x. (Z / c * 2) \<le> g x) F"
hoelzl@50324
  1129
    unfolding filterlim_at_top by auto
hoelzl@50346
  1130
  ultimately show "eventually (\<lambda>x. Z \<le> f x * g x) F"
hoelzl@50324
  1131
  proof eventually_elim
hoelzl@50346
  1132
    fix x assume "c / 2 < f x" "Z / c * 2 \<le> g x"
hoelzl@50346
  1133
    with `0 < Z` `0 < c` have "c / 2 * (Z / c * 2) \<le> f x * g x"
hoelzl@50346
  1134
      by (intro mult_mono) (auto simp: zero_le_divide_iff)
hoelzl@50346
  1135
    with `0 < c` show "Z \<le> f x * g x"
hoelzl@50324
  1136
       by simp
hoelzl@50324
  1137
  qed
hoelzl@50324
  1138
qed
hoelzl@50324
  1139
hoelzl@50324
  1140
lemma filterlim_at_top_mult_at_top: 
hoelzl@50324
  1141
  assumes f: "LIM x F. f x :> at_top"
hoelzl@50324
  1142
  assumes g: "LIM x F. g x :> at_top"
hoelzl@50324
  1143
  shows "LIM x F. (f x * g x :: real) :> at_top"
hoelzl@50324
  1144
  unfolding filterlim_at_top_gt[where c=0]
hoelzl@50324
  1145
proof safe
hoelzl@50324
  1146
  fix Z :: real assume "0 < Z"
hoelzl@50346
  1147
  from f have "eventually (\<lambda>x. 1 \<le> f x) F"
hoelzl@50324
  1148
    unfolding filterlim_at_top by auto
hoelzl@50346
  1149
  moreover from g have "eventually (\<lambda>x. Z \<le> g x) F"
hoelzl@50324
  1150
    unfolding filterlim_at_top by auto
hoelzl@50346
  1151
  ultimately show "eventually (\<lambda>x. Z \<le> f x * g x) F"
hoelzl@50324
  1152
  proof eventually_elim
hoelzl@50346
  1153
    fix x assume "1 \<le> f x" "Z \<le> g x"
hoelzl@50346
  1154
    with `0 < Z` have "1 * Z \<le> f x * g x"
hoelzl@50346
  1155
      by (intro mult_mono) (auto simp: zero_le_divide_iff)
hoelzl@50346
  1156
    then show "Z \<le> f x * g x"
hoelzl@50324
  1157
       by simp
hoelzl@50324
  1158
  qed
hoelzl@50324
  1159
qed
hoelzl@50324
  1160
hoelzl@50419
  1161
lemma filterlim_tendsto_pos_mult_at_bot:
hoelzl@50419
  1162
  assumes "(f ---> c) F" "0 < (c::real)" "filterlim g at_bot F"
hoelzl@50419
  1163
  shows "LIM x F. f x * g x :> at_bot"
hoelzl@50419
  1164
  using filterlim_tendsto_pos_mult_at_top[OF assms(1,2), of "\<lambda>x. - g x"] assms(3)
hoelzl@50419
  1165
  unfolding filterlim_uminus_at_bot by simp
hoelzl@50419
  1166
hoelzl@50324
  1167
lemma filterlim_tendsto_add_at_top: 
hoelzl@50324
  1168
  assumes f: "(f ---> c) F"
hoelzl@50324
  1169
  assumes g: "LIM x F. g x :> at_top"
hoelzl@50324
  1170
  shows "LIM x F. (f x + g x :: real) :> at_top"
hoelzl@50324
  1171
  unfolding filterlim_at_top_gt[where c=0]
hoelzl@50324
  1172
proof safe
hoelzl@50324
  1173
  fix Z :: real assume "0 < Z"
hoelzl@50324
  1174
  from f have "eventually (\<lambda>x. c - 1 < f x) F"
hoelzl@50324
  1175
    by (auto dest!: tendstoD[where e=1] elim!: eventually_elim1 simp: dist_real_def)
hoelzl@50346
  1176
  moreover from g have "eventually (\<lambda>x. Z - (c - 1) \<le> g x) F"
hoelzl@50324
  1177
    unfolding filterlim_at_top by auto
hoelzl@50346
  1178
  ultimately show "eventually (\<lambda>x. Z \<le> f x + g x) F"
hoelzl@50324
  1179
    by eventually_elim simp
hoelzl@50324
  1180
qed
hoelzl@50324
  1181
hoelzl@50347
  1182
lemma LIM_at_top_divide:
hoelzl@50347
  1183
  fixes f g :: "'a \<Rightarrow> real"
hoelzl@50347
  1184
  assumes f: "(f ---> a) F" "0 < a"
hoelzl@50347
  1185
  assumes g: "(g ---> 0) F" "eventually (\<lambda>x. 0 < g x) F"
hoelzl@50347
  1186
  shows "LIM x F. f x / g x :> at_top"
hoelzl@50347
  1187
  unfolding divide_inverse
hoelzl@50347
  1188
  by (rule filterlim_tendsto_pos_mult_at_top[OF f]) (rule filterlim_inverse_at_top[OF g])
hoelzl@50347
  1189
hoelzl@50324
  1190
lemma filterlim_at_top_add_at_top: 
hoelzl@50324
  1191
  assumes f: "LIM x F. f x :> at_top"
hoelzl@50324
  1192
  assumes g: "LIM x F. g x :> at_top"
hoelzl@50324
  1193
  shows "LIM x F. (f x + g x :: real) :> at_top"
hoelzl@50324
  1194
  unfolding filterlim_at_top_gt[where c=0]
hoelzl@50324
  1195
proof safe
hoelzl@50324
  1196
  fix Z :: real assume "0 < Z"
hoelzl@50346
  1197
  from f have "eventually (\<lambda>x. 0 \<le> f x) F"
hoelzl@50324
  1198
    unfolding filterlim_at_top by auto
hoelzl@50346
  1199
  moreover from g have "eventually (\<lambda>x. Z \<le> g x) F"
hoelzl@50324
  1200
    unfolding filterlim_at_top by auto
hoelzl@50346
  1201
  ultimately show "eventually (\<lambda>x. Z \<le> f x + g x) F"
hoelzl@50324
  1202
    by eventually_elim simp
hoelzl@50324
  1203
qed
hoelzl@50324
  1204
hoelzl@50331
  1205
lemma tendsto_divide_0:
hoelzl@50331
  1206
  fixes f :: "_ \<Rightarrow> 'a\<Colon>{real_normed_div_algebra, division_ring_inverse_zero}"
hoelzl@50331
  1207
  assumes f: "(f ---> c) F"
hoelzl@50331
  1208
  assumes g: "LIM x F. g x :> at_infinity"
hoelzl@50331
  1209
  shows "((\<lambda>x. f x / g x) ---> 0) F"
hoelzl@50331
  1210
  using tendsto_mult[OF f filterlim_compose[OF tendsto_inverse_0 g]] by (simp add: divide_inverse)
hoelzl@50331
  1211
hoelzl@50331
  1212
lemma linear_plus_1_le_power:
hoelzl@50331
  1213
  fixes x :: real
hoelzl@50331
  1214
  assumes x: "0 \<le> x"
hoelzl@50331
  1215
  shows "real n * x + 1 \<le> (x + 1) ^ n"
hoelzl@50331
  1216
proof (induct n)
hoelzl@50331
  1217
  case (Suc n)
hoelzl@50331
  1218
  have "real (Suc n) * x + 1 \<le> (x + 1) * (real n * x + 1)"
hoelzl@50331
  1219
    by (simp add: field_simps real_of_nat_Suc mult_nonneg_nonneg x)
hoelzl@50331
  1220
  also have "\<dots> \<le> (x + 1)^Suc n"
hoelzl@50331
  1221
    using Suc x by (simp add: mult_left_mono)
hoelzl@50331
  1222
  finally show ?case .
hoelzl@50331
  1223
qed simp
hoelzl@50331
  1224
hoelzl@50331
  1225
lemma filterlim_realpow_sequentially_gt1:
hoelzl@50331
  1226
  fixes x :: "'a :: real_normed_div_algebra"
hoelzl@50331
  1227
  assumes x[arith]: "1 < norm x"
hoelzl@50331
  1228
  shows "LIM n sequentially. x ^ n :> at_infinity"
hoelzl@50331
  1229
proof (intro filterlim_at_infinity[THEN iffD2] allI impI)
hoelzl@50331
  1230
  fix y :: real assume "0 < y"
hoelzl@50331
  1231
  have "0 < norm x - 1" by simp
hoelzl@50331
  1232
  then obtain N::nat where "y < real N * (norm x - 1)" by (blast dest: reals_Archimedean3)
hoelzl@50331
  1233
  also have "\<dots> \<le> real N * (norm x - 1) + 1" by simp
hoelzl@50331
  1234
  also have "\<dots> \<le> (norm x - 1 + 1) ^ N" by (rule linear_plus_1_le_power) simp
hoelzl@50331
  1235
  also have "\<dots> = norm x ^ N" by simp
hoelzl@50331
  1236
  finally have "\<forall>n\<ge>N. y \<le> norm x ^ n"
hoelzl@50331
  1237
    by (metis order_less_le_trans power_increasing order_less_imp_le x)
hoelzl@50331
  1238
  then show "eventually (\<lambda>n. y \<le> norm (x ^ n)) sequentially"
hoelzl@50331
  1239
    unfolding eventually_sequentially
hoelzl@50331
  1240
    by (auto simp: norm_power)
hoelzl@50331
  1241
qed simp
hoelzl@50331
  1242
hoelzl@51471
  1243
hoelzl@51526
  1244
subsection {* Limits of Sequences *}
hoelzl@51526
  1245
hoelzl@51526
  1246
lemma [trans]: "X=Y ==> Y ----> z ==> X ----> z"
hoelzl@51526
  1247
  by simp
hoelzl@51526
  1248
hoelzl@51526
  1249
lemma LIMSEQ_iff:
hoelzl@51526
  1250
  fixes L :: "'a::real_normed_vector"
hoelzl@51526
  1251
  shows "(X ----> L) = (\<forall>r>0. \<exists>no. \<forall>n \<ge> no. norm (X n - L) < r)"
hoelzl@51526
  1252
unfolding LIMSEQ_def dist_norm ..
hoelzl@51526
  1253
hoelzl@51526
  1254
lemma LIMSEQ_I:
hoelzl@51526
  1255
  fixes L :: "'a::real_normed_vector"
hoelzl@51526
  1256
  shows "(\<And>r. 0 < r \<Longrightarrow> \<exists>no. \<forall>n\<ge>no. norm (X n - L) < r) \<Longrightarrow> X ----> L"
hoelzl@51526
  1257
by (simp add: LIMSEQ_iff)
hoelzl@51526
  1258
hoelzl@51526
  1259
lemma LIMSEQ_D:
hoelzl@51526
  1260
  fixes L :: "'a::real_normed_vector"
hoelzl@51526
  1261
  shows "\<lbrakk>X ----> L; 0 < r\<rbrakk> \<Longrightarrow> \<exists>no. \<forall>n\<ge>no. norm (X n - L) < r"
hoelzl@51526
  1262
by (simp add: LIMSEQ_iff)
hoelzl@51526
  1263
hoelzl@51526
  1264
lemma LIMSEQ_linear: "\<lbrakk> X ----> x ; l > 0 \<rbrakk> \<Longrightarrow> (\<lambda> n. X (n * l)) ----> x"
hoelzl@51526
  1265
  unfolding tendsto_def eventually_sequentially
hoelzl@51526
  1266
  by (metis div_le_dividend div_mult_self1_is_m le_trans nat_mult_commute)
hoelzl@51526
  1267
hoelzl@51526
  1268
lemma Bseq_inverse_lemma:
hoelzl@51526
  1269
  fixes x :: "'a::real_normed_div_algebra"
hoelzl@51526
  1270
  shows "\<lbrakk>r \<le> norm x; 0 < r\<rbrakk> \<Longrightarrow> norm (inverse x) \<le> inverse r"
hoelzl@51526
  1271
apply (subst nonzero_norm_inverse, clarsimp)
hoelzl@51526
  1272
apply (erule (1) le_imp_inverse_le)
hoelzl@51526
  1273
done
hoelzl@51526
  1274
hoelzl@51526
  1275
lemma Bseq_inverse:
hoelzl@51526
  1276
  fixes a :: "'a::real_normed_div_algebra"
hoelzl@51526
  1277
  shows "\<lbrakk>X ----> a; a \<noteq> 0\<rbrakk> \<Longrightarrow> Bseq (\<lambda>n. inverse (X n))"
hoelzl@51526
  1278
  by (rule Bfun_inverse)
hoelzl@51526
  1279
hoelzl@51526
  1280
lemma LIMSEQ_diff_approach_zero:
hoelzl@51526
  1281
  fixes L :: "'a::real_normed_vector"
hoelzl@51526
  1282
  shows "g ----> L ==> (%x. f x - g x) ----> 0 ==> f ----> L"
hoelzl@51526
  1283
  by (drule (1) tendsto_add, simp)
hoelzl@51526
  1284
hoelzl@51526
  1285
lemma LIMSEQ_diff_approach_zero2:
hoelzl@51526
  1286
  fixes L :: "'a::real_normed_vector"
hoelzl@51526
  1287
  shows "f ----> L ==> (%x. f x - g x) ----> 0 ==> g ----> L"
hoelzl@51526
  1288
  by (drule (1) tendsto_diff, simp)
hoelzl@51526
  1289
hoelzl@51526
  1290
text{*An unbounded sequence's inverse tends to 0*}
hoelzl@51526
  1291
hoelzl@51526
  1292
lemma LIMSEQ_inverse_zero:
hoelzl@51526
  1293
  "\<forall>r::real. \<exists>N. \<forall>n\<ge>N. r < X n \<Longrightarrow> (\<lambda>n. inverse (X n)) ----> 0"
hoelzl@51526
  1294
  apply (rule filterlim_compose[OF tendsto_inverse_0])
hoelzl@51526
  1295
  apply (simp add: filterlim_at_infinity[OF order_refl] eventually_sequentially)
hoelzl@51526
  1296
  apply (metis abs_le_D1 linorder_le_cases linorder_not_le)
hoelzl@51526
  1297
  done
hoelzl@51526
  1298
hoelzl@51526
  1299
text{*The sequence @{term "1/n"} tends to 0 as @{term n} tends to infinity*}
hoelzl@51526
  1300
hoelzl@51526
  1301
lemma LIMSEQ_inverse_real_of_nat: "(%n. inverse(real(Suc n))) ----> 0"
hoelzl@51526
  1302
  by (metis filterlim_compose tendsto_inverse_0 filterlim_mono order_refl filterlim_Suc
hoelzl@51526
  1303
            filterlim_compose[OF filterlim_real_sequentially] at_top_le_at_infinity)
hoelzl@51526
  1304
hoelzl@51526
  1305
text{*The sequence @{term "r + 1/n"} tends to @{term r} as @{term n} tends to
hoelzl@51526
  1306
infinity is now easily proved*}
hoelzl@51526
  1307
hoelzl@51526
  1308
lemma LIMSEQ_inverse_real_of_nat_add:
hoelzl@51526
  1309
     "(%n. r + inverse(real(Suc n))) ----> r"
hoelzl@51526
  1310
  using tendsto_add [OF tendsto_const LIMSEQ_inverse_real_of_nat] by auto
hoelzl@51526
  1311
hoelzl@51526
  1312
lemma LIMSEQ_inverse_real_of_nat_add_minus:
hoelzl@51526
  1313
     "(%n. r + -inverse(real(Suc n))) ----> r"
hoelzl@51526
  1314
  using tendsto_add [OF tendsto_const tendsto_minus [OF LIMSEQ_inverse_real_of_nat]]
hoelzl@51526
  1315
  by auto
hoelzl@51526
  1316
hoelzl@51526
  1317
lemma LIMSEQ_inverse_real_of_nat_add_minus_mult:
hoelzl@51526
  1318
     "(%n. r*( 1 + -inverse(real(Suc n)))) ----> r"
hoelzl@51526
  1319
  using tendsto_mult [OF tendsto_const LIMSEQ_inverse_real_of_nat_add_minus [of 1]]
hoelzl@51526
  1320
  by auto
hoelzl@51526
  1321
hoelzl@51526
  1322
subsection {* Convergence on sequences *}
hoelzl@51526
  1323
hoelzl@51526
  1324
lemma convergent_add:
hoelzl@51526
  1325
  fixes X Y :: "nat \<Rightarrow> 'a::real_normed_vector"
hoelzl@51526
  1326
  assumes "convergent (\<lambda>n. X n)"
hoelzl@51526
  1327
  assumes "convergent (\<lambda>n. Y n)"
hoelzl@51526
  1328
  shows "convergent (\<lambda>n. X n + Y n)"
hoelzl@51526
  1329
  using assms unfolding convergent_def by (fast intro: tendsto_add)
hoelzl@51526
  1330
hoelzl@51526
  1331
lemma convergent_setsum:
hoelzl@51526
  1332
  fixes X :: "'a \<Rightarrow> nat \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1333
  assumes "\<And>i. i \<in> A \<Longrightarrow> convergent (\<lambda>n. X i n)"
hoelzl@51526
  1334
  shows "convergent (\<lambda>n. \<Sum>i\<in>A. X i n)"
hoelzl@51526
  1335
proof (cases "finite A")
hoelzl@51526
  1336
  case True from this and assms show ?thesis
hoelzl@51526
  1337
    by (induct A set: finite) (simp_all add: convergent_const convergent_add)
hoelzl@51526
  1338
qed (simp add: convergent_const)
hoelzl@51526
  1339
hoelzl@51526
  1340
lemma (in bounded_linear) convergent:
hoelzl@51526
  1341
  assumes "convergent (\<lambda>n. X n)"
hoelzl@51526
  1342
  shows "convergent (\<lambda>n. f (X n))"
hoelzl@51526
  1343
  using assms unfolding convergent_def by (fast intro: tendsto)
hoelzl@51526
  1344
hoelzl@51526
  1345
lemma (in bounded_bilinear) convergent:
hoelzl@51526
  1346
  assumes "convergent (\<lambda>n. X n)" and "convergent (\<lambda>n. Y n)"
hoelzl@51526
  1347
  shows "convergent (\<lambda>n. X n ** Y n)"
hoelzl@51526
  1348
  using assms unfolding convergent_def by (fast intro: tendsto)
hoelzl@51526
  1349
hoelzl@51526
  1350
lemma convergent_minus_iff:
hoelzl@51526
  1351
  fixes X :: "nat \<Rightarrow> 'a::real_normed_vector"
hoelzl@51526
  1352
  shows "convergent X \<longleftrightarrow> convergent (\<lambda>n. - X n)"
hoelzl@51526
  1353
apply (simp add: convergent_def)
hoelzl@51526
  1354
apply (auto dest: tendsto_minus)
hoelzl@51526
  1355
apply (drule tendsto_minus, auto)
hoelzl@51526
  1356
done
hoelzl@51526
  1357
hoelzl@51526
  1358
hoelzl@51526
  1359
text {* A monotone sequence converges to its least upper bound. *}
hoelzl@51526
  1360
hoelzl@54263
  1361
lemma LIMSEQ_incseq_SUP:
hoelzl@54263
  1362
  fixes X :: "nat \<Rightarrow> 'a::{conditionally_complete_linorder, linorder_topology}"
hoelzl@54263
  1363
  assumes u: "bdd_above (range X)"
hoelzl@54263
  1364
  assumes X: "incseq X"
hoelzl@54263
  1365
  shows "X ----> (SUP i. X i)"
hoelzl@54263
  1366
  by (rule order_tendstoI)
hoelzl@54263
  1367
     (auto simp: eventually_sequentially u less_cSUP_iff intro: X[THEN incseqD] less_le_trans cSUP_lessD[OF u])
hoelzl@51526
  1368
hoelzl@54263
  1369
lemma LIMSEQ_decseq_INF:
hoelzl@54263
  1370
  fixes X :: "nat \<Rightarrow> 'a::{conditionally_complete_linorder, linorder_topology}"
hoelzl@54263
  1371
  assumes u: "bdd_below (range X)"
hoelzl@54263
  1372
  assumes X: "decseq X"
hoelzl@54263
  1373
  shows "X ----> (INF i. X i)"
hoelzl@54263
  1374
  by (rule order_tendstoI)
hoelzl@54263
  1375
     (auto simp: eventually_sequentially u cINF_less_iff intro: X[THEN decseqD] le_less_trans less_cINF_D[OF u])
hoelzl@51526
  1376
hoelzl@51526
  1377
text{*Main monotonicity theorem*}
hoelzl@51526
  1378
hoelzl@51526
  1379
lemma Bseq_monoseq_convergent: "Bseq X \<Longrightarrow> monoseq X \<Longrightarrow> convergent (X::nat\<Rightarrow>real)"
hoelzl@54263
  1380
  by (auto simp: monoseq_iff convergent_def intro: LIMSEQ_decseq_INF LIMSEQ_incseq_SUP dest: Bseq_bdd_above Bseq_bdd_below)
hoelzl@54263
  1381
hoelzl@54263
  1382
lemma Bseq_mono_convergent: "Bseq X \<Longrightarrow> (\<forall>m n. m \<le> n \<longrightarrow> X m \<le> X n) \<Longrightarrow> convergent (X::nat\<Rightarrow>real)"
hoelzl@54263
  1383
  by (auto intro!: Bseq_monoseq_convergent incseq_imp_monoseq simp: incseq_def)
hoelzl@51526
  1384
hoelzl@51526
  1385
lemma Cauchy_iff:
hoelzl@51526
  1386
  fixes X :: "nat \<Rightarrow> 'a::real_normed_vector"
hoelzl@51526
  1387
  shows "Cauchy X \<longleftrightarrow> (\<forall>e>0. \<exists>M. \<forall>m\<ge>M. \<forall>n\<ge>M. norm (X m - X n) < e)"
hoelzl@51526
  1388
  unfolding Cauchy_def dist_norm ..
hoelzl@51526
  1389
hoelzl@51526
  1390
lemma CauchyI:
hoelzl@51526
  1391
  fixes X :: "nat \<Rightarrow> 'a::real_normed_vector"
hoelzl@51526
  1392
  shows "(\<And>e. 0 < e \<Longrightarrow> \<exists>M. \<forall>m\<ge>M. \<forall>n\<ge>M. norm (X m - X n) < e) \<Longrightarrow> Cauchy X"
hoelzl@51526
  1393
by (simp add: Cauchy_iff)
hoelzl@51526
  1394
hoelzl@51526
  1395
lemma CauchyD:
hoelzl@51526
  1396
  fixes X :: "nat \<Rightarrow> 'a::real_normed_vector"
hoelzl@51526
  1397
  shows "\<lbrakk>Cauchy X; 0 < e\<rbrakk> \<Longrightarrow> \<exists>M. \<forall>m\<ge>M. \<forall>n\<ge>M. norm (X m - X n) < e"
hoelzl@51526
  1398
by (simp add: Cauchy_iff)
hoelzl@51526
  1399
hoelzl@51526
  1400
lemma incseq_convergent:
hoelzl@51526
  1401
  fixes X :: "nat \<Rightarrow> real"
hoelzl@51526
  1402
  assumes "incseq X" and "\<forall>i. X i \<le> B"
hoelzl@51526
  1403
  obtains L where "X ----> L" "\<forall>i. X i \<le> L"
hoelzl@51526
  1404
proof atomize_elim
hoelzl@51526
  1405
  from incseq_bounded[OF assms] `incseq X` Bseq_monoseq_convergent[of X]
hoelzl@51526
  1406
  obtain L where "X ----> L"
hoelzl@51526
  1407
    by (auto simp: convergent_def monoseq_def incseq_def)
hoelzl@51526
  1408
  with `incseq X` show "\<exists>L. X ----> L \<and> (\<forall>i. X i \<le> L)"
hoelzl@51526
  1409
    by (auto intro!: exI[of _ L] incseq_le)
hoelzl@51526
  1410
qed
hoelzl@51526
  1411
hoelzl@51526
  1412
lemma decseq_convergent:
hoelzl@51526
  1413
  fixes X :: "nat \<Rightarrow> real"
hoelzl@51526
  1414
  assumes "decseq X" and "\<forall>i. B \<le> X i"
hoelzl@51526
  1415
  obtains L where "X ----> L" "\<forall>i. L \<le> X i"
hoelzl@51526
  1416
proof atomize_elim
hoelzl@51526
  1417
  from decseq_bounded[OF assms] `decseq X` Bseq_monoseq_convergent[of X]
hoelzl@51526
  1418
  obtain L where "X ----> L"
hoelzl@51526
  1419
    by (auto simp: convergent_def monoseq_def decseq_def)
hoelzl@51526
  1420
  with `decseq X` show "\<exists>L. X ----> L \<and> (\<forall>i. L \<le> X i)"
hoelzl@51526
  1421
    by (auto intro!: exI[of _ L] decseq_le)
hoelzl@51526
  1422
qed
hoelzl@51526
  1423
hoelzl@51526
  1424
subsubsection {* Cauchy Sequences are Bounded *}
hoelzl@51526
  1425
hoelzl@51526
  1426
text{*A Cauchy sequence is bounded -- this is the standard
hoelzl@51526
  1427
  proof mechanization rather than the nonstandard proof*}
hoelzl@51526
  1428
hoelzl@51526
  1429
lemma lemmaCauchy: "\<forall>n \<ge> M. norm (X M - X n) < (1::real)
hoelzl@51526
  1430
          ==>  \<forall>n \<ge> M. norm (X n :: 'a::real_normed_vector) < 1 + norm (X M)"
hoelzl@51526
  1431
apply (clarify, drule spec, drule (1) mp)
hoelzl@51526
  1432
apply (simp only: norm_minus_commute)
hoelzl@51526
  1433
apply (drule order_le_less_trans [OF norm_triangle_ineq2])
hoelzl@51526
  1434
apply simp
hoelzl@51526
  1435
done
hoelzl@51526
  1436
hoelzl@51526
  1437
subsection {* Power Sequences *}
hoelzl@51526
  1438
hoelzl@51526
  1439
text{*The sequence @{term "x^n"} tends to 0 if @{term "0\<le>x"} and @{term
hoelzl@51526
  1440
"x<1"}.  Proof will use (NS) Cauchy equivalence for convergence and
hoelzl@51526
  1441
  also fact that bounded and monotonic sequence converges.*}
hoelzl@51526
  1442
hoelzl@51526
  1443
lemma Bseq_realpow: "[| 0 \<le> (x::real); x \<le> 1 |] ==> Bseq (%n. x ^ n)"
hoelzl@51526
  1444
apply (simp add: Bseq_def)
hoelzl@51526
  1445
apply (rule_tac x = 1 in exI)
hoelzl@51526
  1446
apply (simp add: power_abs)
hoelzl@51526
  1447
apply (auto dest: power_mono)
hoelzl@51526
  1448
done
hoelzl@51526
  1449
hoelzl@51526
  1450
lemma monoseq_realpow: fixes x :: real shows "[| 0 \<le> x; x \<le> 1 |] ==> monoseq (%n. x ^ n)"
hoelzl@51526
  1451
apply (clarify intro!: mono_SucI2)
hoelzl@51526
  1452
apply (cut_tac n = n and N = "Suc n" and a = x in power_decreasing, auto)
hoelzl@51526
  1453
done
hoelzl@51526
  1454
hoelzl@51526
  1455
lemma convergent_realpow:
hoelzl@51526
  1456
  "[| 0 \<le> (x::real); x \<le> 1 |] ==> convergent (%n. x ^ n)"
hoelzl@51526
  1457
by (blast intro!: Bseq_monoseq_convergent Bseq_realpow monoseq_realpow)
hoelzl@51526
  1458
hoelzl@51526
  1459
lemma LIMSEQ_inverse_realpow_zero: "1 < (x::real) \<Longrightarrow> (\<lambda>n. inverse (x ^ n)) ----> 0"
hoelzl@51526
  1460
  by (rule filterlim_compose[OF tendsto_inverse_0 filterlim_realpow_sequentially_gt1]) simp
hoelzl@51526
  1461
hoelzl@51526
  1462
lemma LIMSEQ_realpow_zero:
hoelzl@51526
  1463
  "\<lbrakk>0 \<le> (x::real); x < 1\<rbrakk> \<Longrightarrow> (\<lambda>n. x ^ n) ----> 0"
hoelzl@51526
  1464
proof cases
hoelzl@51526
  1465
  assume "0 \<le> x" and "x \<noteq> 0"
hoelzl@51526
  1466
  hence x0: "0 < x" by simp
hoelzl@51526
  1467
  assume x1: "x < 1"
hoelzl@51526
  1468
  from x0 x1 have "1 < inverse x"
hoelzl@51526
  1469
    by (rule one_less_inverse)
hoelzl@51526
  1470
  hence "(\<lambda>n. inverse (inverse x ^ n)) ----> 0"
hoelzl@51526
  1471
    by (rule LIMSEQ_inverse_realpow_zero)
hoelzl@51526
  1472
  thus ?thesis by (simp add: power_inverse)
hoelzl@51526
  1473
qed (rule LIMSEQ_imp_Suc, simp add: tendsto_const)
hoelzl@51526
  1474
hoelzl@51526
  1475
lemma LIMSEQ_power_zero:
hoelzl@51526
  1476
  fixes x :: "'a::{real_normed_algebra_1}"
hoelzl@51526
  1477
  shows "norm x < 1 \<Longrightarrow> (\<lambda>n. x ^ n) ----> 0"
hoelzl@51526
  1478
apply (drule LIMSEQ_realpow_zero [OF norm_ge_zero])
hoelzl@51526
  1479
apply (simp only: tendsto_Zfun_iff, erule Zfun_le)
hoelzl@51526
  1480
apply (simp add: power_abs norm_power_ineq)
hoelzl@51526
  1481
done
hoelzl@51526
  1482
hoelzl@51526
  1483
lemma LIMSEQ_divide_realpow_zero: "1 < x \<Longrightarrow> (\<lambda>n. a / (x ^ n) :: real) ----> 0"
hoelzl@51526
  1484
  by (rule tendsto_divide_0 [OF tendsto_const filterlim_realpow_sequentially_gt1]) simp
hoelzl@51526
  1485
hoelzl@51526
  1486
text{*Limit of @{term "c^n"} for @{term"\<bar>c\<bar> < 1"}*}
hoelzl@51526
  1487
hoelzl@51526
  1488
lemma LIMSEQ_rabs_realpow_zero: "\<bar>c\<bar> < 1 \<Longrightarrow> (\<lambda>n. \<bar>c\<bar> ^ n :: real) ----> 0"
hoelzl@51526
  1489
  by (rule LIMSEQ_realpow_zero [OF abs_ge_zero])
hoelzl@51526
  1490
hoelzl@51526
  1491
lemma LIMSEQ_rabs_realpow_zero2: "\<bar>c\<bar> < 1 \<Longrightarrow> (\<lambda>n. c ^ n :: real) ----> 0"
hoelzl@51526
  1492
  by (rule LIMSEQ_power_zero) simp
hoelzl@51526
  1493
hoelzl@51526
  1494
hoelzl@51526
  1495
subsection {* Limits of Functions *}
hoelzl@51526
  1496
hoelzl@51526
  1497
lemma LIM_eq:
hoelzl@51526
  1498
  fixes a :: "'a::real_normed_vector" and L :: "'b::real_normed_vector"
hoelzl@51526
  1499
  shows "f -- a --> L =
hoelzl@51526
  1500
     (\<forall>r>0.\<exists>s>0.\<forall>x. x \<noteq> a & norm (x-a) < s --> norm (f x - L) < r)"
hoelzl@51526
  1501
by (simp add: LIM_def dist_norm)
hoelzl@51526
  1502
hoelzl@51526
  1503
lemma LIM_I:
hoelzl@51526
  1504
  fixes a :: "'a::real_normed_vector" and L :: "'b::real_normed_vector"
hoelzl@51526
  1505
  shows "(!!r. 0<r ==> \<exists>s>0.\<forall>x. x \<noteq> a & norm (x-a) < s --> norm (f x - L) < r)
hoelzl@51526
  1506
      ==> f -- a --> L"
hoelzl@51526
  1507
by (simp add: LIM_eq)
hoelzl@51526
  1508
hoelzl@51526
  1509
lemma LIM_D:
hoelzl@51526
  1510
  fixes a :: "'a::real_normed_vector" and L :: "'b::real_normed_vector"
hoelzl@51526
  1511
  shows "[| f -- a --> L; 0<r |]
hoelzl@51526
  1512
      ==> \<exists>s>0.\<forall>x. x \<noteq> a & norm (x-a) < s --> norm (f x - L) < r"
hoelzl@51526
  1513
by (simp add: LIM_eq)
hoelzl@51526
  1514
hoelzl@51526
  1515
lemma LIM_offset:
hoelzl@51526
  1516
  fixes a :: "'a::real_normed_vector"
hoelzl@51526
  1517
  shows "f -- a --> L \<Longrightarrow> (\<lambda>x. f (x + k)) -- a - k --> L"
hoelzl@51641
  1518
  unfolding filtermap_at_shift[symmetric, of a k] filterlim_def filtermap_filtermap by simp
hoelzl@51526
  1519
hoelzl@51526
  1520
lemma LIM_offset_zero:
hoelzl@51526
  1521
  fixes a :: "'a::real_normed_vector"
hoelzl@51526
  1522
  shows "f -- a --> L \<Longrightarrow> (\<lambda>h. f (a + h)) -- 0 --> L"
hoelzl@51526
  1523
by (drule_tac k="a" in LIM_offset, simp add: add_commute)
hoelzl@51526
  1524
hoelzl@51526
  1525
lemma LIM_offset_zero_cancel:
hoelzl@51526
  1526
  fixes a :: "'a::real_normed_vector"
hoelzl@51526
  1527
  shows "(\<lambda>h. f (a + h)) -- 0 --> L \<Longrightarrow> f -- a --> L"
hoelzl@51526
  1528
by (drule_tac k="- a" in LIM_offset, simp)
hoelzl@51526
  1529
hoelzl@51642
  1530
lemma LIM_offset_zero_iff:
hoelzl@51642
  1531
  fixes f :: "'a :: real_normed_vector \<Rightarrow> _"
hoelzl@51642
  1532
  shows  "f -- a --> L \<longleftrightarrow> (\<lambda>h. f (a + h)) -- 0 --> L"
hoelzl@51642
  1533
  using LIM_offset_zero_cancel[of f a L] LIM_offset_zero[of f L a] by auto
hoelzl@51642
  1534
hoelzl@51526
  1535
lemma LIM_zero:
hoelzl@51526
  1536
  fixes f :: "'a::topological_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1537
  shows "(f ---> l) F \<Longrightarrow> ((\<lambda>x. f x - l) ---> 0) F"
hoelzl@51526
  1538
unfolding tendsto_iff dist_norm by simp
hoelzl@51526
  1539
hoelzl@51526
  1540
lemma LIM_zero_cancel:
hoelzl@51526
  1541
  fixes f :: "'a::topological_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1542
  shows "((\<lambda>x. f x - l) ---> 0) F \<Longrightarrow> (f ---> l) F"
hoelzl@51526
  1543
unfolding tendsto_iff dist_norm by simp
hoelzl@51526
  1544
hoelzl@51526
  1545
lemma LIM_zero_iff:
hoelzl@51526
  1546
  fixes f :: "'a::metric_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1547
  shows "((\<lambda>x. f x - l) ---> 0) F = (f ---> l) F"
hoelzl@51526
  1548
unfolding tendsto_iff dist_norm by simp
hoelzl@51526
  1549
hoelzl@51526
  1550
lemma LIM_imp_LIM:
hoelzl@51526
  1551
  fixes f :: "'a::topological_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1552
  fixes g :: "'a::topological_space \<Rightarrow> 'c::real_normed_vector"
hoelzl@51526
  1553
  assumes f: "f -- a --> l"
hoelzl@51526
  1554
  assumes le: "\<And>x. x \<noteq> a \<Longrightarrow> norm (g x - m) \<le> norm (f x - l)"
hoelzl@51526
  1555
  shows "g -- a --> m"
hoelzl@51526
  1556
  by (rule metric_LIM_imp_LIM [OF f],
hoelzl@51526
  1557
    simp add: dist_norm le)
hoelzl@51526
  1558
hoelzl@51526
  1559
lemma LIM_equal2:
hoelzl@51526
  1560
  fixes f g :: "'a::real_normed_vector \<Rightarrow> 'b::topological_space"
hoelzl@51526
  1561
  assumes 1: "0 < R"
hoelzl@51526
  1562
  assumes 2: "\<And>x. \<lbrakk>x \<noteq> a; norm (x - a) < R\<rbrakk> \<Longrightarrow> f x = g x"
hoelzl@51526
  1563
  shows "g -- a --> l \<Longrightarrow> f -- a --> l"
hoelzl@51526
  1564
by (rule metric_LIM_equal2 [OF 1 2], simp_all add: dist_norm)
hoelzl@51526
  1565
hoelzl@51526
  1566
lemma LIM_compose2:
hoelzl@51526
  1567
  fixes a :: "'a::real_normed_vector"
hoelzl@51526
  1568
  assumes f: "f -- a --> b"
hoelzl@51526
  1569
  assumes g: "g -- b --> c"
hoelzl@51526
  1570
  assumes inj: "\<exists>d>0. \<forall>x. x \<noteq> a \<and> norm (x - a) < d \<longrightarrow> f x \<noteq> b"
hoelzl@51526
  1571
  shows "(\<lambda>x. g (f x)) -- a --> c"
hoelzl@51526
  1572
by (rule metric_LIM_compose2 [OF f g inj [folded dist_norm]])
hoelzl@51526
  1573
hoelzl@51526
  1574
lemma real_LIM_sandwich_zero:
hoelzl@51526
  1575
  fixes f g :: "'a::topological_space \<Rightarrow> real"
hoelzl@51526
  1576
  assumes f: "f -- a --> 0"
hoelzl@51526
  1577
  assumes 1: "\<And>x. x \<noteq> a \<Longrightarrow> 0 \<le> g x"
hoelzl@51526
  1578
  assumes 2: "\<And>x. x \<noteq> a \<Longrightarrow> g x \<le> f x"
hoelzl@51526
  1579
  shows "g -- a --> 0"
hoelzl@51526
  1580
proof (rule LIM_imp_LIM [OF f]) (* FIXME: use tendsto_sandwich *)
hoelzl@51526
  1581
  fix x assume x: "x \<noteq> a"
hoelzl@51526
  1582
  have "norm (g x - 0) = g x" by (simp add: 1 x)
hoelzl@51526
  1583
  also have "g x \<le> f x" by (rule 2 [OF x])
hoelzl@51526
  1584
  also have "f x \<le> \<bar>f x\<bar>" by (rule abs_ge_self)
hoelzl@51526
  1585
  also have "\<bar>f x\<bar> = norm (f x - 0)" by simp
hoelzl@51526
  1586
  finally show "norm (g x - 0) \<le> norm (f x - 0)" .
hoelzl@51526
  1587
qed
hoelzl@51526
  1588
hoelzl@51526
  1589
hoelzl@51526
  1590
subsection {* Continuity *}
hoelzl@51526
  1591
hoelzl@51526
  1592
lemma LIM_isCont_iff:
hoelzl@51526
  1593
  fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::topological_space"
hoelzl@51526
  1594
  shows "(f -- a --> f a) = ((\<lambda>h. f (a + h)) -- 0 --> f a)"
hoelzl@51526
  1595
by (rule iffI [OF LIM_offset_zero LIM_offset_zero_cancel])
hoelzl@51526
  1596
hoelzl@51526
  1597
lemma isCont_iff:
hoelzl@51526
  1598
  fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::topological_space"
hoelzl@51526
  1599
  shows "isCont f x = (\<lambda>h. f (x + h)) -- 0 --> f x"
hoelzl@51526
  1600
by (simp add: isCont_def LIM_isCont_iff)
hoelzl@51526
  1601
hoelzl@51526
  1602
lemma isCont_LIM_compose2:
hoelzl@51526
  1603
  fixes a :: "'a::real_normed_vector"
hoelzl@51526
  1604
  assumes f [unfolded isCont_def]: "isCont f a"
hoelzl@51526
  1605
  assumes g: "g -- f a --> l"
hoelzl@51526
  1606
  assumes inj: "\<exists>d>0. \<forall>x. x \<noteq> a \<and> norm (x - a) < d \<longrightarrow> f x \<noteq> f a"
hoelzl@51526
  1607
  shows "(\<lambda>x. g (f x)) -- a --> l"
hoelzl@51526
  1608
by (rule LIM_compose2 [OF f g inj])
hoelzl@51526
  1609
hoelzl@51526
  1610
hoelzl@51526
  1611
lemma isCont_norm [simp]:
hoelzl@51526
  1612
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1613
  shows "isCont f a \<Longrightarrow> isCont (\<lambda>x. norm (f x)) a"
hoelzl@51526
  1614
  by (fact continuous_norm)
hoelzl@51526
  1615
hoelzl@51526
  1616
lemma isCont_rabs [simp]:
hoelzl@51526
  1617
  fixes f :: "'a::t2_space \<Rightarrow> real"
hoelzl@51526
  1618
  shows "isCont f a \<Longrightarrow> isCont (\<lambda>x. \<bar>f x\<bar>) a"
hoelzl@51526
  1619
  by (fact continuous_rabs)
hoelzl@51526
  1620
hoelzl@51526
  1621
lemma isCont_add [simp]:
hoelzl@51526
  1622
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1623
  shows "\<lbrakk>isCont f a; isCont g a\<rbrakk> \<Longrightarrow> isCont (\<lambda>x. f x + g x) a"
hoelzl@51526
  1624
  by (fact continuous_add)
hoelzl@51526
  1625
hoelzl@51526
  1626
lemma isCont_minus [simp]:
hoelzl@51526
  1627
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1628
  shows "isCont f a \<Longrightarrow> isCont (\<lambda>x. - f x) a"
hoelzl@51526
  1629
  by (fact continuous_minus)
hoelzl@51526
  1630
hoelzl@51526
  1631
lemma isCont_diff [simp]:
hoelzl@51526
  1632
  fixes f :: "'a::t2_space \<Rightarrow> 'b::real_normed_vector"
hoelzl@51526
  1633
  shows "\<lbrakk>isCont f a; isCont g a\<rbrakk> \<Longrightarrow> isCont (\<lambda>x. f x - g x) a"
hoelzl@51526
  1634
  by (fact continuous_diff)
hoelzl@51526
  1635
hoelzl@51526
  1636
lemma isCont_mult [simp]:
hoelzl@51526
  1637
  fixes f g :: "'a::t2_space \<Rightarrow> 'b::real_normed_algebra"
hoelzl@51526
  1638
  shows "\<lbrakk>isCont f a; isCont g a\<rbrakk> \<Longrightarrow> isCont (\<lambda>x. f x * g x) a"
hoelzl@51526
  1639
  by (fact continuous_mult)
hoelzl@51526
  1640
hoelzl@51526
  1641
lemma (in bounded_linear) isCont:
hoelzl@51526
  1642
  "isCont g a \<Longrightarrow> isCont (\<lambda>x. f (g x)) a"
hoelzl@51526
  1643
  by (fact continuous)
hoelzl@51526
  1644
hoelzl@51526
  1645
lemma (in bounded_bilinear) isCont:
hoelzl@51526
  1646
  "\<lbrakk>isCont f a; isCont g a\<rbrakk> \<Longrightarrow> isCont (\<lambda>x. f x ** g x) a"
hoelzl@51526
  1647
  by (fact continuous)
hoelzl@51526
  1648
hoelzl@51526
  1649
lemmas isCont_scaleR [simp] = 
hoelzl@51526
  1650
  bounded_bilinear.isCont [OF bounded_bilinear_scaleR]
hoelzl@51526
  1651
hoelzl@51526
  1652
lemmas isCont_of_real [simp] =
hoelzl@51526
  1653
  bounded_linear.isCont [OF bounded_linear_of_real]
hoelzl@51526
  1654
hoelzl@51526
  1655
lemma isCont_power [simp]:
hoelzl@51526
  1656
  fixes f :: "'a::t2_space \<Rightarrow> 'b::{power,real_normed_algebra}"
hoelzl@51526
  1657
  shows "isCont f a \<Longrightarrow> isCont (\<lambda>x. f x ^ n) a"
hoelzl@51526
  1658
  by (fact continuous_power)
hoelzl@51526
  1659
hoelzl@51526
  1660
lemma isCont_setsum [simp]:
hoelzl@51526
  1661
  fixes f :: "'a \<Rightarrow> 'b::t2_space \<Rightarrow> 'c::real_normed_vector"
hoelzl@51526
  1662
  shows "\<forall>i\<in>A. isCont (f i) a \<Longrightarrow> isCont (\<lambda>x. \<Sum>i\<in>A. f i x) a"
hoelzl@51526
  1663
  by (auto intro: continuous_setsum)
hoelzl@51526
  1664
hoelzl@51526
  1665
lemmas isCont_intros =
hoelzl@51526
  1666
  isCont_ident isCont_const isCont_norm isCont_rabs isCont_add isCont_minus
hoelzl@51526
  1667
  isCont_diff isCont_mult isCont_inverse isCont_divide isCont_scaleR
hoelzl@51526
  1668
  isCont_of_real isCont_power isCont_sgn isCont_setsum
hoelzl@51526
  1669
hoelzl@51526
  1670
subsection {* Uniform Continuity *}
hoelzl@51526
  1671
hoelzl@51531
  1672
definition
hoelzl@51531
  1673
  isUCont :: "['a::metric_space \<Rightarrow> 'b::metric_space] \<Rightarrow> bool" where
hoelzl@51531
  1674
  "isUCont f = (\<forall>r>0. \<exists>s>0. \<forall>x y. dist x y < s \<longrightarrow> dist (f x) (f y) < r)"
hoelzl@51531
  1675
hoelzl@51531
  1676
lemma isUCont_isCont: "isUCont f ==> isCont f x"
hoelzl@51531
  1677
by (simp add: isUCont_def isCont_def LIM_def, force)
hoelzl@51531
  1678
hoelzl@51531
  1679
lemma isUCont_Cauchy:
hoelzl@51531
  1680
  "\<lbrakk>isUCont f; Cauchy X\<rbrakk> \<Longrightarrow> Cauchy (\<lambda>n. f (X n))"
hoelzl@51531
  1681
unfolding isUCont_def
hoelzl@51531
  1682
apply (rule metric_CauchyI)
hoelzl@51531
  1683
apply (drule_tac x=e in spec, safe)
hoelzl@51531
  1684
apply (drule_tac e=s in metric_CauchyD, safe)
hoelzl@51531
  1685
apply (rule_tac x=M in exI, simp)
hoelzl@51531
  1686
done
hoelzl@51531
  1687
hoelzl@51526
  1688
lemma (in bounded_linear) isUCont: "isUCont f"
hoelzl@51526
  1689
unfolding isUCont_def dist_norm
hoelzl@51526
  1690
proof (intro allI impI)
hoelzl@51526
  1691
  fix r::real assume r: "0 < r"
hoelzl@51526
  1692
  obtain K where K: "0 < K" and norm_le: "\<And>x. norm (f x) \<le> norm x * K"
hoelzl@51526
  1693
    using pos_bounded by fast
hoelzl@51526
  1694
  show "\<exists>s>0. \<forall>x y. norm (x - y) < s \<longrightarrow> norm (f x - f y) < r"
hoelzl@51526
  1695
  proof (rule exI, safe)
hoelzl@51526
  1696
    from r K show "0 < r / K" by (rule divide_pos_pos)
hoelzl@51526
  1697
  next
hoelzl@51526
  1698
    fix x y :: 'a
hoelzl@51526
  1699
    assume xy: "norm (x - y) < r / K"
hoelzl@51526
  1700
    have "norm (f x - f y) = norm (f (x - y))" by (simp only: diff)
hoelzl@51526
  1701
    also have "\<dots> \<le> norm (x - y) * K" by (rule norm_le)
hoelzl@51526
  1702
    also from K xy have "\<dots> < r" by (simp only: pos_less_divide_eq)
hoelzl@51526
  1703
    finally show "norm (f x - f y) < r" .
hoelzl@51526
  1704
  qed
hoelzl@51526
  1705
qed
hoelzl@51526
  1706
hoelzl@51526
  1707
lemma (in bounded_linear) Cauchy: "Cauchy X \<Longrightarrow> Cauchy (\<lambda>n. f (X n))"
hoelzl@51526
  1708
by (rule isUCont [THEN isUCont_Cauchy])
hoelzl@51526
  1709
hoelzl@51526
  1710
lemma LIM_less_bound: 
hoelzl@51526
  1711
  fixes f :: "real \<Rightarrow> real"
hoelzl@51526
  1712
  assumes ev: "b < x" "\<forall> x' \<in> { b <..< x}. 0 \<le> f x'" and "isCont f x"
hoelzl@51526
  1713
  shows "0 \<le> f x"
hoelzl@51526
  1714
proof (rule tendsto_le_const)
hoelzl@51526
  1715
  show "(f ---> f x) (at_left x)"
hoelzl@51526
  1716
    using `isCont f x` by (simp add: filterlim_at_split isCont_def)
hoelzl@51526
  1717
  show "eventually (\<lambda>x. 0 \<le> f x) (at_left x)"
hoelzl@51641
  1718
    using ev by (auto simp: eventually_at dist_real_def intro!: exI[of _ "x - b"])
hoelzl@51526
  1719
qed simp
hoelzl@51471
  1720
hoelzl@51529
  1721
hoelzl@51529
  1722
subsection {* Nested Intervals and Bisection -- Needed for Compactness *}
hoelzl@51529
  1723
hoelzl@51529
  1724
lemma nested_sequence_unique:
hoelzl@51529
  1725
  assumes "\<forall>n. f n \<le> f (Suc n)" "\<forall>n. g (Suc n) \<le> g n" "\<forall>n. f n \<le> g n" "(\<lambda>n. f n - g n) ----> 0"
hoelzl@51529
  1726
  shows "\<exists>l::real. ((\<forall>n. f n \<le> l) \<and> f ----> l) \<and> ((\<forall>n. l \<le> g n) \<and> g ----> l)"
hoelzl@51529
  1727
proof -
hoelzl@51529
  1728
  have "incseq f" unfolding incseq_Suc_iff by fact
hoelzl@51529
  1729
  have "decseq g" unfolding decseq_Suc_iff by fact
hoelzl@51529
  1730
hoelzl@51529
  1731
  { fix n
hoelzl@51529
  1732
    from `decseq g` have "g n \<le> g 0" by (rule decseqD) simp
hoelzl@51529
  1733
    with `\<forall>n. f n \<le> g n`[THEN spec, of n] have "f n \<le> g 0" by auto }
hoelzl@51529
  1734
  then obtain u where "f ----> u" "\<forall>i. f i \<le> u"
hoelzl@51529
  1735
    using incseq_convergent[OF `incseq f`] by auto
hoelzl@51529
  1736
  moreover
hoelzl@51529
  1737
  { fix n
hoelzl@51529
  1738
    from `incseq f` have "f 0 \<le> f n" by (rule incseqD) simp
hoelzl@51529
  1739
    with `\<forall>n. f n \<le> g n`[THEN spec, of n] have "f 0 \<le> g n" by simp }
hoelzl@51529
  1740
  then obtain l where "g ----> l" "\<forall>i. l \<le> g i"
hoelzl@51529
  1741
    using decseq_convergent[OF `decseq g`] by auto
hoelzl@51529
  1742
  moreover note LIMSEQ_unique[OF assms(4) tendsto_diff[OF `f ----> u` `g ----> l`]]
hoelzl@51529
  1743
  ultimately show ?thesis by auto
hoelzl@51529
  1744
qed
hoelzl@51529
  1745
hoelzl@51529
  1746
lemma Bolzano[consumes 1, case_names trans local]:
hoelzl@51529
  1747
  fixes P :: "real \<Rightarrow> real \<Rightarrow> bool"
hoelzl@51529
  1748
  assumes [arith]: "a \<le> b"
hoelzl@51529
  1749
  assumes trans: "\<And>a b c. \<lbrakk>P a b; P b c; a \<le> b; b \<le> c\<rbrakk> \<Longrightarrow> P a c"
hoelzl@51529
  1750
  assumes local: "\<And>x. a \<le> x \<Longrightarrow> x \<le> b \<Longrightarrow> \<exists>d>0. \<forall>a b. a \<le> x \<and> x \<le> b \<and> b - a < d \<longrightarrow> P a b"
hoelzl@51529
  1751
  shows "P a b"
hoelzl@51529
  1752
proof -
blanchet@55415
  1753
  def bisect \<equiv> "rec_nat (a, b) (\<lambda>n (x, y). if P x ((x+y) / 2) then ((x+y)/2, y) else (x, (x+y)/2))"
hoelzl@51529
  1754
  def l \<equiv> "\<lambda>n. fst (bisect n)" and u \<equiv> "\<lambda>n. snd (bisect n)"
hoelzl@51529
  1755
  have l[simp]: "l 0 = a" "\<And>n. l (Suc n) = (if P (l n) ((l n + u n) / 2) then (l n + u n) / 2 else l n)"
hoelzl@51529
  1756
    and u[simp]: "u 0 = b" "\<And>n. u (Suc n) = (if P (l n) ((l n + u n) / 2) then u n else (l n + u n) / 2)"
hoelzl@51529
  1757
    by (simp_all add: l_def u_def bisect_def split: prod.split)
hoelzl@51529
  1758
hoelzl@51529
  1759
  { fix n have "l n \<le> u n" by (induct n) auto } note this[simp]
hoelzl@51529
  1760
hoelzl@51529
  1761
  have "\<exists>x. ((\<forall>n. l n \<le> x) \<and> l ----> x) \<and> ((\<forall>n. x \<le> u n) \<and> u ----> x)"
hoelzl@51529
  1762
  proof (safe intro!: nested_sequence_unique)
hoelzl@51529
  1763
    fix n show "l n \<le> l (Suc n)" "u (Suc n) \<le> u n" by (induct n) auto
hoelzl@51529
  1764
  next
hoelzl@51529
  1765
    { fix n have "l n - u n = (a - b) / 2^n" by (induct n) (auto simp: field_simps) }
hoelzl@51529
  1766
    then show "(\<lambda>n. l n - u n) ----> 0" by (simp add: LIMSEQ_divide_realpow_zero)
hoelzl@51529
  1767
  qed fact
hoelzl@51529
  1768
  then obtain x where x: "\<And>n. l n \<le> x" "\<And>n. x \<le> u n" and "l ----> x" "u ----> x" by auto
hoelzl@51529
  1769
  obtain d where "0 < d" and d: "\<And>a b. a \<le> x \<Longrightarrow> x \<le> b \<Longrightarrow> b - a < d \<Longrightarrow> P a b"
hoelzl@51529
  1770
    using `l 0 \<le> x` `x \<le> u 0` local[of x] by auto
hoelzl@51529
  1771
hoelzl@51529
  1772
  show "P a b"
hoelzl@51529
  1773
  proof (rule ccontr)
hoelzl@51529
  1774
    assume "\<not> P a b" 
hoelzl@51529
  1775
    { fix n have "\<not> P (l n) (u n)"
hoelzl@51529
  1776
      proof (induct n)
hoelzl@51529
  1777
        case (Suc n) with trans[of "l n" "(l n + u n) / 2" "u n"] show ?case by auto
hoelzl@51529
  1778
      qed (simp add: `\<not> P a b`) }
hoelzl@51529
  1779
    moreover
hoelzl@51529
  1780
    { have "eventually (\<lambda>n. x - d / 2 < l n) sequentially"
hoelzl@51529
  1781
        using `0 < d` `l ----> x` by (intro order_tendstoD[of _ x]) auto
hoelzl@51529
  1782
      moreover have "eventually (\<lambda>n. u n < x + d / 2) sequentially"
hoelzl@51529
  1783
        using `0 < d` `u ----> x` by (intro order_tendstoD[of _ x]) auto
hoelzl@51529
  1784
      ultimately have "eventually (\<lambda>n. P (l n) (u n)) sequentially"
hoelzl@51529
  1785
      proof eventually_elim
hoelzl@51529
  1786
        fix n assume "x - d / 2 < l n" "u n < x + d / 2"
hoelzl@51529
  1787
        from add_strict_mono[OF this] have "u n - l n < d" by simp
hoelzl@51529
  1788
        with x show "P (l n) (u n)" by (rule d)
hoelzl@51529
  1789
      qed }
hoelzl@51529
  1790
    ultimately show False by simp
hoelzl@51529
  1791
  qed
hoelzl@51529
  1792
qed
hoelzl@51529
  1793
hoelzl@51529
  1794
lemma compact_Icc[simp, intro]: "compact {a .. b::real}"
hoelzl@51529
  1795
proof (cases "a \<le> b", rule compactI)
hoelzl@51529
  1796
  fix C assume C: "a \<le> b" "\<forall>t\<in>C. open t" "{a..b} \<subseteq> \<Union>C"
hoelzl@51529
  1797
  def T == "{a .. b}"
hoelzl@51529
  1798
  from C(1,3) show "\<exists>C'\<subseteq>C. finite C' \<and> {a..b} \<subseteq> \<Union>C'"
hoelzl@51529
  1799
  proof (induct rule: Bolzano)
hoelzl@51529
  1800
    case (trans a b c)
hoelzl@51529
  1801
    then have *: "{a .. c} = {a .. b} \<union> {b .. c}" by auto
hoelzl@51529
  1802
    from trans obtain C1 C2 where "C1\<subseteq>C \<and> finite C1 \<and> {a..b} \<subseteq> \<Union>C1" "C2\<subseteq>C \<and> finite C2 \<and> {b..c} \<subseteq> \<Union>C2"
hoelzl@51529
  1803
      by (auto simp: *)
hoelzl@51529
  1804
    with trans show ?case
hoelzl@51529
  1805
      unfolding * by (intro exI[of _ "C1 \<union> C2"]) auto
hoelzl@51529
  1806
  next
hoelzl@51529
  1807
    case (local x)
hoelzl@51529
  1808
    then have "x \<in> \<Union>C" using C by auto
hoelzl@51529
  1809
    with C(2) obtain c where "x \<in> c" "open c" "c \<in> C" by auto
hoelzl@51529
  1810
    then obtain e where "0 < e" "{x - e <..< x + e} \<subseteq> c"
hoelzl@51529
  1811
      by (auto simp: open_real_def dist_real_def subset_eq Ball_def abs_less_iff)
hoelzl@51529
  1812
    with `c \<in> C` show ?case
hoelzl@51529
  1813
      by (safe intro!: exI[of _ "e/2"] exI[of _ "{c}"]) auto
hoelzl@51529
  1814
  qed
hoelzl@51529
  1815
qed simp
hoelzl@51529
  1816
hoelzl@51529
  1817
hoelzl@51529
  1818
subsection {* Boundedness of continuous functions *}
hoelzl@51529
  1819
hoelzl@51529
  1820
text{*By bisection, function continuous on closed interval is bounded above*}
hoelzl@51529
  1821
hoelzl@51529
  1822
lemma isCont_eq_Ub:
hoelzl@51529
  1823
  fixes f :: "real \<Rightarrow> 'a::linorder_topology"
hoelzl@51529
  1824
  shows "a \<le> b \<Longrightarrow> \<forall>x::real. a \<le> x \<and> x \<le> b \<longrightarrow> isCont f x \<Longrightarrow>
hoelzl@51529
  1825
    \<exists>M. (\<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> f x \<le> M) \<and> (\<exists>x. a \<le> x \<and> x \<le> b \<and> f x = M)"
hoelzl@51529
  1826
  using continuous_attains_sup[of "{a .. b}" f]
hoelzl@51529
  1827
  by (auto simp add: continuous_at_imp_continuous_on Ball_def Bex_def)
hoelzl@51529
  1828
hoelzl@51529
  1829
lemma isCont_eq_Lb:
hoelzl@51529
  1830
  fixes f :: "real \<Rightarrow> 'a::linorder_topology"
hoelzl@51529
  1831
  shows "a \<le> b \<Longrightarrow> \<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> isCont f x \<Longrightarrow>
hoelzl@51529
  1832
    \<exists>M. (\<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> M \<le> f x) \<and> (\<exists>x. a \<le> x \<and> x \<le> b \<and> f x = M)"
hoelzl@51529
  1833
  using continuous_attains_inf[of "{a .. b}" f]
hoelzl@51529
  1834
  by (auto simp add: continuous_at_imp_continuous_on Ball_def Bex_def)
hoelzl@51529
  1835
hoelzl@51529
  1836
lemma isCont_bounded:
hoelzl@51529
  1837
  fixes f :: "real \<Rightarrow> 'a::linorder_topology"
hoelzl@51529
  1838
  shows "a \<le> b \<Longrightarrow> \<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> isCont f x \<Longrightarrow> \<exists>M. \<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> f x \<le> M"
hoelzl@51529
  1839
  using isCont_eq_Ub[of a b f] by auto
hoelzl@51529
  1840
hoelzl@51529
  1841
lemma isCont_has_Ub:
hoelzl@51529
  1842
  fixes f :: "real \<Rightarrow> 'a::linorder_topology"
hoelzl@51529
  1843
  shows "a \<le> b \<Longrightarrow> \<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> isCont f x \<Longrightarrow>
hoelzl@51529
  1844
    \<exists>M. (\<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> f x \<le> M) \<and> (\<forall>N. N < M \<longrightarrow> (\<exists>x. a \<le> x \<and> x \<le> b \<and> N < f x))"
hoelzl@51529
  1845
  using isCont_eq_Ub[of a b f] by auto
hoelzl@51529
  1846
hoelzl@51529
  1847
(*HOL style here: object-level formulations*)
hoelzl@51529
  1848
lemma IVT_objl: "(f(a::real) \<le> (y::real) & y \<le> f(b) & a \<le> b &
hoelzl@51529
  1849
      (\<forall>x. a \<le> x & x \<le> b --> isCont f x))
hoelzl@51529
  1850
      --> (\<exists>x. a \<le> x & x \<le> b & f(x) = y)"
hoelzl@51529
  1851
  by (blast intro: IVT)
hoelzl@51529
  1852
hoelzl@51529
  1853
lemma IVT2_objl: "(f(b::real) \<le> (y::real) & y \<le> f(a) & a \<le> b &
hoelzl@51529
  1854
      (\<forall>x. a \<le> x & x \<le> b --> isCont f x))
hoelzl@51529
  1855
      --> (\<exists>x. a \<le> x & x \<le> b & f(x) = y)"
hoelzl@51529
  1856
  by (blast intro: IVT2)
hoelzl@51529
  1857
hoelzl@51529
  1858
lemma isCont_Lb_Ub:
hoelzl@51529
  1859
  fixes f :: "real \<Rightarrow> real"
hoelzl@51529
  1860
  assumes "a \<le> b" "\<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> isCont f x"
hoelzl@51529
  1861
  shows "\<exists>L M. (\<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> L \<le> f x \<and> f x \<le> M) \<and> 
hoelzl@51529
  1862
               (\<forall>y. L \<le> y \<and> y \<le> M \<longrightarrow> (\<exists>x. a \<le> x \<and> x \<le> b \<and> (f x = y)))"
hoelzl@51529
  1863
proof -
hoelzl@51529
  1864
  obtain M where M: "a \<le> M" "M \<le> b" "\<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> f x \<le> f M"
hoelzl@51529
  1865
    using isCont_eq_Ub[OF assms] by auto
hoelzl@51529
  1866
  obtain L where L: "a \<le> L" "L \<le> b" "\<forall>x. a \<le> x \<and> x \<le> b \<longrightarrow> f L \<le> f x"
hoelzl@51529
  1867
    using isCont_eq_Lb[OF assms] by auto
hoelzl@51529
  1868
  show ?thesis
hoelzl@51529
  1869
    using IVT[of f L _ M] IVT2[of f L _ M] M L assms
hoelzl@51529
  1870
    apply (rule_tac x="f L" in exI)
hoelzl@51529
  1871
    apply (rule_tac x="f M" in exI)
hoelzl@51529
  1872
    apply (cases "L \<le> M")
hoelzl@51529
  1873
    apply (simp, metis order_trans)
hoelzl@51529
  1874
    apply (simp, metis order_trans)
hoelzl@51529
  1875
    done
hoelzl@51529
  1876
qed
hoelzl@51529
  1877
hoelzl@51529
  1878
hoelzl@51529
  1879
text{*Continuity of inverse function*}
hoelzl@51529
  1880
hoelzl@51529
  1881
lemma isCont_inverse_function:
hoelzl@51529
  1882
  fixes f g :: "real \<Rightarrow> real"
hoelzl@51529
  1883
  assumes d: "0 < d"
hoelzl@51529
  1884
      and inj: "\<forall>z. \<bar>z-x\<bar> \<le> d \<longrightarrow> g (f z) = z"
hoelzl@51529
  1885
      and cont: "\<forall>z. \<bar>z-x\<bar> \<le> d \<longrightarrow> isCont f z"
hoelzl@51529
  1886
  shows "isCont g (f x)"
hoelzl@51529
  1887
proof -
hoelzl@51529
  1888
  let ?A = "f (x - d)" and ?B = "f (x + d)" and ?D = "{x - d..x + d}"
hoelzl@51529
  1889
hoelzl@51529
  1890
  have f: "continuous_on ?D f"
hoelzl@51529
  1891
    using cont by (intro continuous_at_imp_continuous_on ballI) auto
hoelzl@51529
  1892
  then have g: "continuous_on (f`?D) g"
hoelzl@51529
  1893
    using inj by (intro continuous_on_inv) auto
hoelzl@51529
  1894
hoelzl@51529
  1895
  from d f have "{min ?A ?B <..< max ?A ?B} \<subseteq> f ` ?D"
hoelzl@51529
  1896
    by (intro connected_contains_Ioo connected_continuous_image) (auto split: split_min split_max)
hoelzl@51529
  1897
  with g have "continuous_on {min ?A ?B <..< max ?A ?B} g"
hoelzl@51529
  1898
    by (rule continuous_on_subset)
hoelzl@51529
  1899
  moreover
hoelzl@51529
  1900
  have "(?A < f x \<and> f x < ?B) \<or> (?B < f x \<and> f x < ?A)"
hoelzl@51529
  1901
    using d inj by (intro continuous_inj_imp_mono[OF _ _ f] inj_on_imageI2[of g, OF inj_onI]) auto
hoelzl@51529
  1902
  then have "f x \<in> {min ?A ?B <..< max ?A ?B}"
hoelzl@51529
  1903
    by auto
hoelzl@51529
  1904
  ultimately
hoelzl@51529
  1905
  show ?thesis
hoelzl@51529
  1906
    by (simp add: continuous_on_eq_continuous_at)
hoelzl@51529
  1907
qed
hoelzl@51529
  1908
hoelzl@51529
  1909
lemma isCont_inverse_function2:
hoelzl@51529
  1910
  fixes f g :: "real \<Rightarrow> real" shows
hoelzl@51529
  1911
  "\<lbrakk>a < x; x < b;
hoelzl@51529
  1912
    \<forall>z. a \<le> z \<and> z \<le> b \<longrightarrow> g (f z) = z;
hoelzl@51529
  1913
    \<forall>z. a \<le> z \<and> z \<le> b \<longrightarrow> isCont f z\<rbrakk>
hoelzl@51529
  1914
   \<Longrightarrow> isCont g (f x)"
hoelzl@51529
  1915
apply (rule isCont_inverse_function
hoelzl@51529
  1916
       [where f=f and d="min (x - a) (b - x)"])
hoelzl@51529
  1917
apply (simp_all add: abs_le_iff)
hoelzl@51529
  1918
done
hoelzl@51529
  1919
hoelzl@51529
  1920
(* need to rename second isCont_inverse *)
hoelzl@51529
  1921
hoelzl@51529
  1922
lemma isCont_inv_fun:
hoelzl@51529
  1923
  fixes f g :: "real \<Rightarrow> real"
hoelzl@51529
  1924
  shows "[| 0 < d; \<forall>z. \<bar>z - x\<bar> \<le> d --> g(f(z)) = z;  
hoelzl@51529
  1925
         \<forall>z. \<bar>z - x\<bar> \<le> d --> isCont f z |]  
hoelzl@51529
  1926
      ==> isCont g (f x)"
hoelzl@51529
  1927
by (rule isCont_inverse_function)
hoelzl@51529
  1928
hoelzl@51529
  1929
text{*Bartle/Sherbert: Introduction to Real Analysis, Theorem 4.2.9, p. 110*}
hoelzl@51529
  1930
lemma LIM_fun_gt_zero:
hoelzl@51529
  1931
  fixes f :: "real \<Rightarrow> real"
hoelzl@51529
  1932
  shows "f -- c --> l \<Longrightarrow> 0 < l \<Longrightarrow> \<exists>r. 0 < r \<and> (\<forall>x. x \<noteq> c \<and> \<bar>c - x\<bar> < r \<longrightarrow> 0 < f x)"
hoelzl@51529
  1933
apply (drule (1) LIM_D, clarify)
hoelzl@51529
  1934
apply (rule_tac x = s in exI)
hoelzl@51529
  1935
apply (simp add: abs_less_iff)
hoelzl@51529
  1936
done
hoelzl@51529
  1937
hoelzl@51529
  1938
lemma LIM_fun_less_zero:
hoelzl@51529
  1939
  fixes f :: "real \<Rightarrow> real"
hoelzl@51529
  1940
  shows "f -- c --> l \<Longrightarrow> l < 0 \<Longrightarrow> \<exists>r. 0 < r \<and> (\<forall>x. x \<noteq> c \<and> \<bar>c - x\<bar> < r \<longrightarrow> f x < 0)"
hoelzl@51529
  1941
apply (drule LIM_D [where r="-l"], simp, clarify)
hoelzl@51529
  1942
apply (rule_tac x = s in exI)
hoelzl@51529
  1943
apply (simp add: abs_less_iff)
hoelzl@51529
  1944
done
hoelzl@51529
  1945
hoelzl@51529
  1946
lemma LIM_fun_not_zero:
hoelzl@51529
  1947
  fixes f :: "real \<Rightarrow> real"
hoelzl@51529
  1948
  shows "f -- c --> l \<Longrightarrow> l \<noteq> 0 \<Longrightarrow> \<exists>r. 0 < r \<and> (\<forall>x. x \<noteq> c \<and> \<bar>c - x\<bar> < r \<longrightarrow> f x \<noteq> 0)"
hoelzl@51529
  1949
  using LIM_fun_gt_zero[of f l c] LIM_fun_less_zero[of f l c] by (auto simp add: neq_iff)
hoelzl@51531
  1950
huffman@31349
  1951
end
hoelzl@50324
  1952