src/HOL/Multivariate_Analysis/Complex_Analysis_Basics.thy
author paulson <lp15@cam.ac.uk>
Mon Mar 07 15:57:02 2016 +0000 (2016-03-07)
changeset 62534 6855b348e828
parent 62533 bc25f3916a99
child 62540 f2fc5485e3b0
permissions -rw-r--r--
complex_differentiable -> field_differentiable, etc. (making these theorems also available for type real)
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(*  Author: John Harrison, Marco Maggesi, Graziano Gentili, Gianni Ciolli, Valentina Bruno
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    Ported from "hol_light/Multivariate/canal.ml" by L C Paulson (2014)
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*)
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section \<open>Complex Analysis Basics\<close>
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theory Complex_Analysis_Basics
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imports Cartesian_Euclidean_Space "~~/src/HOL/Library/Nonpos_Ints"
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begin
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subsection\<open>General lemmas\<close>
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lemma nonneg_Reals_cmod_eq_Re: "z \<in> \<real>\<^sub>\<ge>\<^sub>0 \<Longrightarrow> norm z = Re z"
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  by (simp add: complex_nonneg_Reals_iff cmod_eq_Re)
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lemma has_derivative_mult_right:
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  fixes c:: "'a :: real_normed_algebra"
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  shows "((op * c) has_derivative (op * c)) F"
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by (rule has_derivative_mult_right [OF has_derivative_id])
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lemma has_derivative_of_real[derivative_intros, simp]:
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  "(f has_derivative f') F \<Longrightarrow> ((\<lambda>x. of_real (f x)) has_derivative (\<lambda>x. of_real (f' x))) F"
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  using bounded_linear.has_derivative[OF bounded_linear_of_real] .
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lemma has_vector_derivative_real_complex:
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  "DERIV f (of_real a) :> f' \<Longrightarrow> ((\<lambda>x. f (of_real x)) has_vector_derivative f') (at a within s)"
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  using has_derivative_compose[of of_real of_real a _ f "op * f'"]
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  by (simp add: scaleR_conv_of_real ac_simps has_vector_derivative_def has_field_derivative_def)
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lemma fact_cancel:
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  fixes c :: "'a::real_field"
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  shows "of_nat (Suc n) * c / (fact (Suc n)) = c / (fact n)"
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  by (simp add: of_nat_mult del: of_nat_Suc times_nat.simps)
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lemma bilinear_times:
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  fixes c::"'a::real_algebra" shows "bilinear (\<lambda>x y::'a. x*y)"
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  by (auto simp: bilinear_def distrib_left distrib_right intro!: linearI)
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lemma linear_cnj: "linear cnj"
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  using bounded_linear.linear[OF bounded_linear_cnj] .
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lemma tendsto_Re_upper:
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  assumes "~ (trivial_limit F)"
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          "(f \<longlongrightarrow> l) F"
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          "eventually (\<lambda>x. Re(f x) \<le> b) F"
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    shows  "Re(l) \<le> b"
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  by (metis assms tendsto_le [OF _ tendsto_const]  tendsto_Re)
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lemma tendsto_Re_lower:
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  assumes "~ (trivial_limit F)"
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          "(f \<longlongrightarrow> l) F"
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          "eventually (\<lambda>x. b \<le> Re(f x)) F"
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    shows  "b \<le> Re(l)"
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  by (metis assms tendsto_le [OF _ _ tendsto_const]  tendsto_Re)
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lemma tendsto_Im_upper:
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  assumes "~ (trivial_limit F)"
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          "(f \<longlongrightarrow> l) F"
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          "eventually (\<lambda>x. Im(f x) \<le> b) F"
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    shows  "Im(l) \<le> b"
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  by (metis assms tendsto_le [OF _ tendsto_const]  tendsto_Im)
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lemma tendsto_Im_lower:
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  assumes "~ (trivial_limit F)"
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          "(f \<longlongrightarrow> l) F"
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          "eventually (\<lambda>x. b \<le> Im(f x)) F"
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    shows  "b \<le> Im(l)"
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  by (metis assms tendsto_le [OF _ _ tendsto_const]  tendsto_Im)
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lemma lambda_zero: "(\<lambda>h::'a::mult_zero. 0) = op * 0"
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  by auto
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lemma lambda_one: "(\<lambda>x::'a::monoid_mult. x) = op * 1"
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  by auto
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lemma continuous_mult_left:
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  fixes c::"'a::real_normed_algebra"
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  shows "continuous F f \<Longrightarrow> continuous F (\<lambda>x. c * f x)"
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by (rule continuous_mult [OF continuous_const])
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lemma continuous_mult_right:
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  fixes c::"'a::real_normed_algebra"
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  shows "continuous F f \<Longrightarrow> continuous F (\<lambda>x. f x * c)"
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by (rule continuous_mult [OF _ continuous_const])
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lemma continuous_on_mult_left:
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  fixes c::"'a::real_normed_algebra"
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  shows "continuous_on s f \<Longrightarrow> continuous_on s (\<lambda>x. c * f x)"
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by (rule continuous_on_mult [OF continuous_on_const])
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lemma continuous_on_mult_right:
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  fixes c::"'a::real_normed_algebra"
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  shows "continuous_on s f \<Longrightarrow> continuous_on s (\<lambda>x. f x * c)"
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by (rule continuous_on_mult [OF _ continuous_on_const])
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lemma uniformly_continuous_on_cmul_right [continuous_intros]:
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  fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::real_normed_algebra"
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  shows "uniformly_continuous_on s f \<Longrightarrow> uniformly_continuous_on s (\<lambda>x. f x * c)"
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  using bounded_linear.uniformly_continuous_on[OF bounded_linear_mult_left] .
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lemma uniformly_continuous_on_cmul_left[continuous_intros]:
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  fixes f :: "'a::real_normed_vector \<Rightarrow> 'b::real_normed_algebra"
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  assumes "uniformly_continuous_on s f"
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    shows "uniformly_continuous_on s (\<lambda>x. c * f x)"
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by (metis assms bounded_linear.uniformly_continuous_on bounded_linear_mult_right)
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lemma continuous_within_norm_id [continuous_intros]: "continuous (at x within S) norm"
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  by (rule continuous_norm [OF continuous_ident])
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lemma continuous_on_norm_id [continuous_intros]: "continuous_on S norm"
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  by (intro continuous_on_id continuous_on_norm)
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subsection\<open>DERIV stuff\<close>
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lemma DERIV_zero_connected_constant:
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  fixes f :: "'a::{real_normed_field,euclidean_space} \<Rightarrow> 'a"
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  assumes "connected s"
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      and "open s"
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      and "finite k"
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      and "continuous_on s f"
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      and "\<forall>x\<in>(s - k). DERIV f x :> 0"
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    obtains c where "\<And>x. x \<in> s \<Longrightarrow> f(x) = c"
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using has_derivative_zero_connected_constant [OF assms(1-4)] assms
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by (metis DERIV_const has_derivative_const Diff_iff at_within_open frechet_derivative_at has_field_derivative_def)
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lemma DERIV_zero_constant:
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  fixes f :: "'a::{real_normed_field, real_inner} \<Rightarrow> 'a"
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  shows    "\<lbrakk>convex s;
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             \<And>x. x\<in>s \<Longrightarrow> (f has_field_derivative 0) (at x within s)\<rbrakk>
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             \<Longrightarrow> \<exists>c. \<forall>x \<in> s. f(x) = c"
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  by (auto simp: has_field_derivative_def lambda_zero intro: has_derivative_zero_constant)
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lemma DERIV_zero_unique:
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  fixes f :: "'a::{real_normed_field, real_inner} \<Rightarrow> 'a"
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  assumes "convex s"
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      and d0: "\<And>x. x\<in>s \<Longrightarrow> (f has_field_derivative 0) (at x within s)"
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      and "a \<in> s"
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      and "x \<in> s"
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    shows "f x = f a"
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  by (rule has_derivative_zero_unique [OF assms(1) _ assms(4,3)])
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     (metis d0 has_field_derivative_imp_has_derivative lambda_zero)
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lemma DERIV_zero_connected_unique:
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  fixes f :: "'a::{real_normed_field, real_inner} \<Rightarrow> 'a"
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  assumes "connected s"
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      and "open s"
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      and d0: "\<And>x. x\<in>s \<Longrightarrow> DERIV f x :> 0"
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      and "a \<in> s"
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      and "x \<in> s"
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    shows "f x = f a"
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    by (rule has_derivative_zero_unique_connected [OF assms(2,1) _ assms(5,4)])
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       (metis has_field_derivative_def lambda_zero d0)
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lemma DERIV_transform_within:
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  assumes "(f has_field_derivative f') (at a within s)"
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      and "0 < d" "a \<in> s"
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      and "\<And>x. x\<in>s \<Longrightarrow> dist x a < d \<Longrightarrow> f x = g x"
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    shows "(g has_field_derivative f') (at a within s)"
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  using assms unfolding has_field_derivative_def
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  by (blast intro: has_derivative_transform_within)
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lemma DERIV_transform_within_open:
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  assumes "DERIV f a :> f'"
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      and "open s" "a \<in> s"
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      and "\<And>x. x\<in>s \<Longrightarrow> f x = g x"
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    shows "DERIV g a :> f'"
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  using assms unfolding has_field_derivative_def
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by (metis has_derivative_transform_within_open)
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lemma DERIV_transform_at:
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  assumes "DERIV f a :> f'"
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      and "0 < d"
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      and "\<And>x. dist x a < d \<Longrightarrow> f x = g x"
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    shows "DERIV g a :> f'"
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  by (blast intro: assms DERIV_transform_within)
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(*generalising DERIV_isconst_all, which requires type real (using the ordering)*)
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lemma DERIV_zero_UNIV_unique:
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  fixes f :: "'a::{real_normed_field, real_inner} \<Rightarrow> 'a"
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  shows "(\<And>x. DERIV f x :> 0) \<Longrightarrow> f x = f a"
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by (metis DERIV_zero_unique UNIV_I assms convex_UNIV)
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subsection \<open>Some limit theorems about real part of real series etc.\<close>
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(*MOVE? But not to Finite_Cartesian_Product*)
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lemma sums_vec_nth :
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  assumes "f sums a"
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  shows "(\<lambda>x. f x $ i) sums a $ i"
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using assms unfolding sums_def
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by (auto dest: tendsto_vec_nth [where i=i])
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lemma summable_vec_nth :
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  assumes "summable f"
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  shows "summable (\<lambda>x. f x $ i)"
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using assms unfolding summable_def
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by (blast intro: sums_vec_nth)
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subsection \<open>Complex number lemmas\<close>
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lemma
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  shows open_halfspace_Re_lt: "open {z. Re(z) < b}"
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    and open_halfspace_Re_gt: "open {z. Re(z) > b}"
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    and closed_halfspace_Re_ge: "closed {z. Re(z) \<ge> b}"
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    and closed_halfspace_Re_le: "closed {z. Re(z) \<le> b}"
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    and closed_halfspace_Re_eq: "closed {z. Re(z) = b}"
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    and open_halfspace_Im_lt: "open {z. Im(z) < b}"
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    and open_halfspace_Im_gt: "open {z. Im(z) > b}"
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    and closed_halfspace_Im_ge: "closed {z. Im(z) \<ge> b}"
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    and closed_halfspace_Im_le: "closed {z. Im(z) \<le> b}"
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    and closed_halfspace_Im_eq: "closed {z. Im(z) = b}"
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  by (intro open_Collect_less closed_Collect_le closed_Collect_eq isCont_Re
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            isCont_Im continuous_ident continuous_const)+
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lemma closed_complex_Reals: "closed (\<real> :: complex set)"
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proof -
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  have "(\<real> :: complex set) = {z. Im z = 0}"
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    by (auto simp: complex_is_Real_iff)
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  then show ?thesis
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    by (metis closed_halfspace_Im_eq)
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qed
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lemma closed_Real_halfspace_Re_le: "closed (\<real> \<inter> {w. Re w \<le> x})"
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  by (simp add: closed_Int closed_complex_Reals closed_halfspace_Re_le)
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corollary closed_nonpos_Reals_complex [simp]: "closed (\<real>\<^sub>\<le>\<^sub>0 :: complex set)"
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proof -
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  have "\<real>\<^sub>\<le>\<^sub>0 = \<real> \<inter> {z. Re(z) \<le> 0}"
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    using complex_nonpos_Reals_iff complex_is_Real_iff by auto
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  then show ?thesis
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    by (metis closed_Real_halfspace_Re_le)
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qed
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lemma closed_Real_halfspace_Re_ge: "closed (\<real> \<inter> {w. x \<le> Re(w)})"
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  using closed_halfspace_Re_ge
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  by (simp add: closed_Int closed_complex_Reals)
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corollary closed_nonneg_Reals_complex [simp]: "closed (\<real>\<^sub>\<ge>\<^sub>0 :: complex set)"
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proof -
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  have "\<real>\<^sub>\<ge>\<^sub>0 = \<real> \<inter> {z. Re(z) \<ge> 0}"
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    using complex_nonneg_Reals_iff complex_is_Real_iff by auto
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  then show ?thesis
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    by (metis closed_Real_halfspace_Re_ge)
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qed
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lemma closed_real_abs_le: "closed {w \<in> \<real>. \<bar>Re w\<bar> \<le> r}"
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proof -
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  have "{w \<in> \<real>. \<bar>Re w\<bar> \<le> r} = (\<real> \<inter> {w. Re w \<le> r}) \<inter> (\<real> \<inter> {w. Re w \<ge> -r})"
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    by auto
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  then show "closed {w \<in> \<real>. \<bar>Re w\<bar> \<le> r}"
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    by (simp add: closed_Int closed_Real_halfspace_Re_ge closed_Real_halfspace_Re_le)
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qed
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lemma real_lim:
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  fixes l::complex
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  assumes "(f \<longlongrightarrow> l) F" and "~(trivial_limit F)" and "eventually P F" and "\<And>a. P a \<Longrightarrow> f a \<in> \<real>"
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  shows  "l \<in> \<real>"
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proof (rule Lim_in_closed_set[OF closed_complex_Reals _ assms(2,1)])
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  show "eventually (\<lambda>x. f x \<in> \<real>) F"
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    using assms(3, 4) by (auto intro: eventually_mono)
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qed
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lemma real_lim_sequentially:
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  fixes l::complex
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  shows "(f \<longlongrightarrow> l) sequentially \<Longrightarrow> (\<exists>N. \<forall>n\<ge>N. f n \<in> \<real>) \<Longrightarrow> l \<in> \<real>"
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by (rule real_lim [where F=sequentially]) (auto simp: eventually_sequentially)
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lemma real_series:
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  fixes l::complex
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  shows "f sums l \<Longrightarrow> (\<And>n. f n \<in> \<real>) \<Longrightarrow> l \<in> \<real>"
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unfolding sums_def
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by (metis real_lim_sequentially setsum_in_Reals)
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lemma Lim_null_comparison_Re:
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  assumes "eventually (\<lambda>x. norm(f x) \<le> Re(g x)) F" "(g \<longlongrightarrow> 0) F" shows "(f \<longlongrightarrow> 0) F"
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  by (rule Lim_null_comparison[OF assms(1)] tendsto_eq_intros assms(2))+ simp
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subsection\<open>Holomorphic functions\<close>
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definition field_differentiable :: "['a \<Rightarrow> 'a::real_normed_field, 'a filter] \<Rightarrow> bool"
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           (infixr "(field'_differentiable)" 50)
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  where "f field_differentiable F \<equiv> \<exists>f'. (f has_field_derivative f') F"
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lemma field_differentiable_derivI:
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    "f field_differentiable (at x) \<Longrightarrow> (f has_field_derivative deriv f x) (at x)"
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by (simp add: field_differentiable_def DERIV_deriv_iff_has_field_derivative)
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lemma field_differentiable_imp_continuous_at:
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   289
    "f field_differentiable (at x within s) \<Longrightarrow> continuous (at x within s) f"
lp15@62534
   290
  by (metis DERIV_continuous field_differentiable_def)
lp15@56215
   291
lp15@62534
   292
lemma field_differentiable_within_subset:
lp15@62534
   293
    "\<lbrakk>f field_differentiable (at x within s); t \<subseteq> s\<rbrakk>
lp15@62534
   294
     \<Longrightarrow> f field_differentiable (at x within t)"
lp15@62534
   295
  by (metis DERIV_subset field_differentiable_def)
lp15@56215
   296
lp15@62534
   297
lemma field_differentiable_at_within:
lp15@62534
   298
    "\<lbrakk>f field_differentiable (at x)\<rbrakk>
lp15@62534
   299
     \<Longrightarrow> f field_differentiable (at x within s)"
lp15@62534
   300
  unfolding field_differentiable_def
lp15@56215
   301
  by (metis DERIV_subset top_greatest)
lp15@56215
   302
lp15@62534
   303
lemma field_differentiable_linear [simp,derivative_intros]: "(op * c) field_differentiable F"
lp15@56215
   304
proof -
hoelzl@56370
   305
  show ?thesis
lp15@62534
   306
    unfolding field_differentiable_def has_field_derivative_def mult_commute_abs
lp15@56215
   307
    by (force intro: has_derivative_mult_right)
lp15@56215
   308
qed
lp15@56215
   309
lp15@62534
   310
lemma field_differentiable_const [simp,derivative_intros]: "(\<lambda>z. c) field_differentiable F"
lp15@62534
   311
  unfolding field_differentiable_def has_field_derivative_def
hoelzl@56369
   312
  by (rule exI [where x=0])
lp15@61609
   313
     (metis has_derivative_const lambda_zero)
lp15@56215
   314
lp15@62534
   315
lemma field_differentiable_ident [simp,derivative_intros]: "(\<lambda>z. z) field_differentiable F"
lp15@62534
   316
  unfolding field_differentiable_def has_field_derivative_def
hoelzl@56369
   317
  by (rule exI [where x=1])
hoelzl@56369
   318
     (simp add: lambda_one [symmetric])
lp15@56215
   319
lp15@62534
   320
lemma field_differentiable_id [simp,derivative_intros]: "id field_differentiable F"
lp15@62534
   321
  unfolding id_def by (rule field_differentiable_ident)
hoelzl@56370
   322
lp15@62534
   323
lemma field_differentiable_minus [derivative_intros]:
lp15@62534
   324
  "f field_differentiable F \<Longrightarrow> (\<lambda>z. - (f z)) field_differentiable F"
lp15@62534
   325
  using assms unfolding field_differentiable_def
lp15@56215
   326
  by (metis field_differentiable_minus)
lp15@56215
   327
lp15@62534
   328
lemma field_differentiable_add [derivative_intros]:
lp15@62534
   329
  assumes "f field_differentiable F" "g field_differentiable F"
lp15@62534
   330
    shows "(\<lambda>z. f z + g z) field_differentiable F"
lp15@62534
   331
  using assms unfolding field_differentiable_def
lp15@56215
   332
  by (metis field_differentiable_add)
lp15@56215
   333
lp15@62534
   334
lemma field_differentiable_add_const [simp,derivative_intros]:
lp15@62534
   335
     "op + c field_differentiable F"
lp15@62534
   336
  by (simp add: field_differentiable_add)
lp15@62533
   337
lp15@62534
   338
lemma field_differentiable_setsum [derivative_intros]:
lp15@62534
   339
  "(\<And>i. i \<in> I \<Longrightarrow> (f i) field_differentiable F) \<Longrightarrow> (\<lambda>z. \<Sum>i\<in>I. f i z) field_differentiable F"
hoelzl@56370
   340
  by (induct I rule: infinite_finite_induct)
lp15@62534
   341
     (auto intro: field_differentiable_add field_differentiable_const)
hoelzl@56370
   342
lp15@62534
   343
lemma field_differentiable_diff [derivative_intros]:
lp15@62534
   344
  assumes "f field_differentiable F" "g field_differentiable F"
lp15@62534
   345
    shows "(\<lambda>z. f z - g z) field_differentiable F"
lp15@62534
   346
  using assms unfolding field_differentiable_def
lp15@56215
   347
  by (metis field_differentiable_diff)
lp15@56215
   348
lp15@62534
   349
lemma field_differentiable_inverse [derivative_intros]:
lp15@62534
   350
  assumes "f field_differentiable (at a within s)" "f a \<noteq> 0"
lp15@62534
   351
  shows "(\<lambda>z. inverse (f z)) field_differentiable (at a within s)"
lp15@62534
   352
  using assms unfolding field_differentiable_def
lp15@56215
   353
  by (metis DERIV_inverse_fun)
lp15@56215
   354
lp15@62534
   355
lemma field_differentiable_mult [derivative_intros]:
lp15@62534
   356
  assumes "f field_differentiable (at a within s)"
lp15@62534
   357
          "g field_differentiable (at a within s)"
lp15@62534
   358
    shows "(\<lambda>z. f z * g z) field_differentiable (at a within s)"
lp15@62534
   359
  using assms unfolding field_differentiable_def
lp15@56215
   360
  by (metis DERIV_mult [of f _ a s g])
lp15@61609
   361
lp15@62534
   362
lemma field_differentiable_divide [derivative_intros]:
lp15@62534
   363
  assumes "f field_differentiable (at a within s)"
lp15@62534
   364
          "g field_differentiable (at a within s)"
lp15@56215
   365
          "g a \<noteq> 0"
lp15@62534
   366
    shows "(\<lambda>z. f z / g z) field_differentiable (at a within s)"
lp15@62534
   367
  using assms unfolding field_differentiable_def
lp15@56215
   368
  by (metis DERIV_divide [of f _ a s g])
lp15@56215
   369
lp15@62534
   370
lemma field_differentiable_power [derivative_intros]:
lp15@62534
   371
  assumes "f field_differentiable (at a within s)"
lp15@62534
   372
    shows "(\<lambda>z. f z ^ n) field_differentiable (at a within s)"
lp15@62534
   373
  using assms unfolding field_differentiable_def
lp15@56215
   374
  by (metis DERIV_power)
lp15@56215
   375
lp15@62534
   376
lemma field_differentiable_transform_within:
lp15@56215
   377
  "0 < d \<Longrightarrow>
lp15@56215
   378
        x \<in> s \<Longrightarrow>
lp15@56215
   379
        (\<And>x'. x' \<in> s \<Longrightarrow> dist x' x < d \<Longrightarrow> f x' = g x') \<Longrightarrow>
lp15@62534
   380
        f field_differentiable (at x within s)
lp15@62534
   381
        \<Longrightarrow> g field_differentiable (at x within s)"
lp15@62534
   382
  unfolding field_differentiable_def has_field_derivative_def
lp15@56215
   383
  by (blast intro: has_derivative_transform_within)
lp15@56215
   384
lp15@62534
   385
lemma field_differentiable_compose_within:
lp15@62534
   386
  assumes "f field_differentiable (at a within s)"
lp15@62534
   387
          "g field_differentiable (at (f a) within f`s)"
lp15@62534
   388
    shows "(g o f) field_differentiable (at a within s)"
lp15@62534
   389
  using assms unfolding field_differentiable_def
lp15@56215
   390
  by (metis DERIV_image_chain)
lp15@56215
   391
lp15@62534
   392
lemma field_differentiable_compose:
lp15@62534
   393
  "f field_differentiable at z \<Longrightarrow> g field_differentiable at (f z)
lp15@62534
   394
          \<Longrightarrow> (g o f) field_differentiable at z"
lp15@62534
   395
by (metis field_differentiable_at_within field_differentiable_compose_within)
hoelzl@56370
   396
lp15@62534
   397
lemma field_differentiable_within_open:
lp15@62534
   398
     "\<lbrakk>a \<in> s; open s\<rbrakk> \<Longrightarrow> f field_differentiable at a within s \<longleftrightarrow>
lp15@62534
   399
                          f field_differentiable at a"
lp15@62534
   400
  unfolding field_differentiable_def
lp15@56215
   401
  by (metis at_within_open)
lp15@56215
   402
lp15@62408
   403
subsection\<open>Caratheodory characterization\<close>
lp15@56215
   404
lp15@62534
   405
lemma field_differentiable_caratheodory_at:
lp15@62534
   406
  "f field_differentiable (at z) \<longleftrightarrow>
lp15@56215
   407
         (\<exists>g. (\<forall>w. f(w) - f(z) = g(w) * (w - z)) \<and> continuous (at z) g)"
lp15@56215
   408
  using CARAT_DERIV [of f]
lp15@62534
   409
  by (simp add: field_differentiable_def has_field_derivative_def)
lp15@56215
   410
lp15@62534
   411
lemma field_differentiable_caratheodory_within:
lp15@62534
   412
  "f field_differentiable (at z within s) \<longleftrightarrow>
lp15@56215
   413
         (\<exists>g. (\<forall>w. f(w) - f(z) = g(w) * (w - z)) \<and> continuous (at z within s) g)"
lp15@56215
   414
  using DERIV_caratheodory_within [of f]
lp15@62534
   415
  by (simp add: field_differentiable_def has_field_derivative_def)
lp15@56215
   416
wenzelm@60420
   417
subsection\<open>Holomorphic\<close>
hoelzl@56370
   418
hoelzl@56370
   419
definition holomorphic_on :: "[complex \<Rightarrow> complex, complex set] \<Rightarrow> bool"
hoelzl@56370
   420
           (infixl "(holomorphic'_on)" 50)
lp15@62534
   421
  where "f holomorphic_on s \<equiv> \<forall>x\<in>s. f field_differentiable (at x within s)"
lp15@61609
   422
lp15@61520
   423
named_theorems holomorphic_intros "structural introduction rules for holomorphic_on"
lp15@61520
   424
lp15@62534
   425
lemma holomorphic_onI [intro?]: "(\<And>x. x \<in> s \<Longrightarrow> f field_differentiable (at x within s)) \<Longrightarrow> f holomorphic_on s"
paulson@62131
   426
  by (simp add: holomorphic_on_def)
paulson@62131
   427
lp15@62534
   428
lemma holomorphic_onD [dest?]: "\<lbrakk>f holomorphic_on s; x \<in> s\<rbrakk> \<Longrightarrow> f field_differentiable (at x within s)"
paulson@62131
   429
  by (simp add: holomorphic_on_def)
paulson@62131
   430
paulson@62131
   431
lemma holomorphic_on_imp_differentiable_at:
lp15@62534
   432
   "\<lbrakk>f holomorphic_on s; open s; x \<in> s\<rbrakk> \<Longrightarrow> f field_differentiable (at x)"
paulson@62131
   433
using at_within_open holomorphic_on_def by fastforce
paulson@62131
   434
lp15@61520
   435
lemma holomorphic_on_empty [holomorphic_intros]: "f holomorphic_on {}"
hoelzl@56370
   436
  by (simp add: holomorphic_on_def)
hoelzl@56370
   437
hoelzl@56370
   438
lemma holomorphic_on_open:
hoelzl@56370
   439
    "open s \<Longrightarrow> f holomorphic_on s \<longleftrightarrow> (\<forall>x \<in> s. \<exists>f'. DERIV f x :> f')"
lp15@62534
   440
  by (auto simp: holomorphic_on_def field_differentiable_def has_field_derivative_def at_within_open [of _ s])
hoelzl@56370
   441
lp15@61609
   442
lemma holomorphic_on_imp_continuous_on:
hoelzl@56370
   443
    "f holomorphic_on s \<Longrightarrow> continuous_on s f"
lp15@62534
   444
  by (metis field_differentiable_imp_continuous_at continuous_on_eq_continuous_within holomorphic_on_def)
hoelzl@56370
   445
hoelzl@56370
   446
lemma holomorphic_on_subset:
hoelzl@56370
   447
    "f holomorphic_on s \<Longrightarrow> t \<subseteq> s \<Longrightarrow> f holomorphic_on t"
hoelzl@56370
   448
  unfolding holomorphic_on_def
lp15@62534
   449
  by (metis field_differentiable_within_subset subsetD)
hoelzl@56370
   450
hoelzl@56370
   451
lemma holomorphic_transform: "\<lbrakk>f holomorphic_on s; \<And>x. x \<in> s \<Longrightarrow> f x = g x\<rbrakk> \<Longrightarrow> g holomorphic_on s"
lp15@62534
   452
  by (metis field_differentiable_transform_within linordered_field_no_ub holomorphic_on_def)
hoelzl@56370
   453
hoelzl@56370
   454
lemma holomorphic_cong: "s = t ==> (\<And>x. x \<in> s \<Longrightarrow> f x = g x) \<Longrightarrow> f holomorphic_on s \<longleftrightarrow> g holomorphic_on t"
hoelzl@56370
   455
  by (metis holomorphic_transform)
hoelzl@56370
   456
lp15@62217
   457
lemma holomorphic_on_linear [simp, holomorphic_intros]: "(op * c) holomorphic_on s"
lp15@62534
   458
  unfolding holomorphic_on_def by (metis field_differentiable_linear)
hoelzl@56370
   459
lp15@62217
   460
lemma holomorphic_on_const [simp, holomorphic_intros]: "(\<lambda>z. c) holomorphic_on s"
lp15@62534
   461
  unfolding holomorphic_on_def by (metis field_differentiable_const)
hoelzl@56370
   462
lp15@62217
   463
lemma holomorphic_on_ident [simp, holomorphic_intros]: "(\<lambda>x. x) holomorphic_on s"
lp15@62534
   464
  unfolding holomorphic_on_def by (metis field_differentiable_ident)
hoelzl@56370
   465
lp15@62217
   466
lemma holomorphic_on_id [simp, holomorphic_intros]: "id holomorphic_on s"
hoelzl@56370
   467
  unfolding id_def by (rule holomorphic_on_ident)
hoelzl@56370
   468
hoelzl@56370
   469
lemma holomorphic_on_compose:
hoelzl@56370
   470
  "f holomorphic_on s \<Longrightarrow> g holomorphic_on (f ` s) \<Longrightarrow> (g o f) holomorphic_on s"
lp15@62534
   471
  using field_differentiable_compose_within[of f _ s g]
hoelzl@56370
   472
  by (auto simp: holomorphic_on_def)
hoelzl@56370
   473
hoelzl@56370
   474
lemma holomorphic_on_compose_gen:
hoelzl@56370
   475
  "f holomorphic_on s \<Longrightarrow> g holomorphic_on t \<Longrightarrow> f ` s \<subseteq> t \<Longrightarrow> (g o f) holomorphic_on s"
hoelzl@56370
   476
  by (metis holomorphic_on_compose holomorphic_on_subset)
hoelzl@56370
   477
lp15@61520
   478
lemma holomorphic_on_minus [holomorphic_intros]: "f holomorphic_on s \<Longrightarrow> (\<lambda>z. -(f z)) holomorphic_on s"
lp15@62534
   479
  by (metis field_differentiable_minus holomorphic_on_def)
hoelzl@56370
   480
lp15@61520
   481
lemma holomorphic_on_add [holomorphic_intros]:
hoelzl@56370
   482
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s\<rbrakk> \<Longrightarrow> (\<lambda>z. f z + g z) holomorphic_on s"
lp15@62534
   483
  unfolding holomorphic_on_def by (metis field_differentiable_add)
hoelzl@56370
   484
lp15@61520
   485
lemma holomorphic_on_diff [holomorphic_intros]:
hoelzl@56370
   486
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s\<rbrakk> \<Longrightarrow> (\<lambda>z. f z - g z) holomorphic_on s"
lp15@62534
   487
  unfolding holomorphic_on_def by (metis field_differentiable_diff)
hoelzl@56370
   488
lp15@61520
   489
lemma holomorphic_on_mult [holomorphic_intros]:
hoelzl@56370
   490
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s\<rbrakk> \<Longrightarrow> (\<lambda>z. f z * g z) holomorphic_on s"
lp15@62534
   491
  unfolding holomorphic_on_def by (metis field_differentiable_mult)
hoelzl@56370
   492
lp15@61520
   493
lemma holomorphic_on_inverse [holomorphic_intros]:
hoelzl@56370
   494
  "\<lbrakk>f holomorphic_on s; \<And>z. z \<in> s \<Longrightarrow> f z \<noteq> 0\<rbrakk> \<Longrightarrow> (\<lambda>z. inverse (f z)) holomorphic_on s"
lp15@62534
   495
  unfolding holomorphic_on_def by (metis field_differentiable_inverse)
hoelzl@56370
   496
lp15@61520
   497
lemma holomorphic_on_divide [holomorphic_intros]:
hoelzl@56370
   498
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s; \<And>z. z \<in> s \<Longrightarrow> g z \<noteq> 0\<rbrakk> \<Longrightarrow> (\<lambda>z. f z / g z) holomorphic_on s"
lp15@62534
   499
  unfolding holomorphic_on_def by (metis field_differentiable_divide)
hoelzl@56370
   500
lp15@61520
   501
lemma holomorphic_on_power [holomorphic_intros]:
hoelzl@56370
   502
  "f holomorphic_on s \<Longrightarrow> (\<lambda>z. (f z)^n) holomorphic_on s"
lp15@62534
   503
  unfolding holomorphic_on_def by (metis field_differentiable_power)
hoelzl@56370
   504
lp15@61520
   505
lemma holomorphic_on_setsum [holomorphic_intros]:
hoelzl@56370
   506
  "(\<And>i. i \<in> I \<Longrightarrow> (f i) holomorphic_on s) \<Longrightarrow> (\<lambda>x. setsum (\<lambda>i. f i x) I) holomorphic_on s"
lp15@62534
   507
  unfolding holomorphic_on_def by (metis field_differentiable_setsum)
hoelzl@56370
   508
lp15@62534
   509
lemma DERIV_deriv_iff_field_differentiable:
lp15@62534
   510
  "DERIV f x :> deriv f x \<longleftrightarrow> f field_differentiable at x"
lp15@62534
   511
  unfolding field_differentiable_def by (metis DERIV_imp_deriv)
hoelzl@56370
   512
lp15@62533
   513
lemma holomorphic_derivI:
lp15@62533
   514
     "\<lbrakk>f holomorphic_on S; open S; x \<in> S\<rbrakk>
lp15@62533
   515
      \<Longrightarrow> (f has_field_derivative deriv f x) (at x within T)"
lp15@62534
   516
by (metis DERIV_deriv_iff_field_differentiable at_within_open  holomorphic_on_def has_field_derivative_at_within)
lp15@62533
   517
hoelzl@56370
   518
lemma complex_derivative_chain:
lp15@62534
   519
  "f field_differentiable at x \<Longrightarrow> g field_differentiable at (f x)
hoelzl@56370
   520
    \<Longrightarrow> deriv (g o f) x = deriv g (f x) * deriv f x"
lp15@62534
   521
  by (metis DERIV_deriv_iff_field_differentiable DERIV_chain DERIV_imp_deriv)
hoelzl@56370
   522
lp15@62397
   523
lemma deriv_linear [simp]: "deriv (\<lambda>w. c * w) = (\<lambda>z. c)"
hoelzl@56370
   524
  by (metis DERIV_imp_deriv DERIV_cmult_Id)
hoelzl@56370
   525
lp15@62397
   526
lemma deriv_ident [simp]: "deriv (\<lambda>w. w) = (\<lambda>z. 1)"
hoelzl@56370
   527
  by (metis DERIV_imp_deriv DERIV_ident)
hoelzl@56370
   528
lp15@62397
   529
lemma deriv_id [simp]: "deriv id = (\<lambda>z. 1)"
lp15@62397
   530
  by (simp add: id_def)
lp15@62397
   531
lp15@62397
   532
lemma deriv_const [simp]: "deriv (\<lambda>w. c) = (\<lambda>z. 0)"
hoelzl@56370
   533
  by (metis DERIV_imp_deriv DERIV_const)
hoelzl@56370
   534
lp15@62534
   535
lemma deriv_add [simp]:
lp15@62534
   536
  "\<lbrakk>f field_differentiable at z; g field_differentiable at z\<rbrakk>
hoelzl@56370
   537
   \<Longrightarrow> deriv (\<lambda>w. f w + g w) z = deriv f z + deriv g z"
lp15@62534
   538
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   539
  by (auto intro!: DERIV_imp_deriv derivative_intros)
hoelzl@56370
   540
lp15@62534
   541
lemma deriv_diff [simp]:
lp15@62534
   542
  "\<lbrakk>f field_differentiable at z; g field_differentiable at z\<rbrakk>
hoelzl@56370
   543
   \<Longrightarrow> deriv (\<lambda>w. f w - g w) z = deriv f z - deriv g z"
lp15@62534
   544
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   545
  by (auto intro!: DERIV_imp_deriv derivative_intros)
hoelzl@56370
   546
lp15@62534
   547
lemma deriv_mult [simp]:
lp15@62534
   548
  "\<lbrakk>f field_differentiable at z; g field_differentiable at z\<rbrakk>
hoelzl@56370
   549
   \<Longrightarrow> deriv (\<lambda>w. f w * g w) z = f z * deriv g z + deriv f z * g z"
lp15@62534
   550
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   551
  by (auto intro!: DERIV_imp_deriv derivative_eq_intros)
hoelzl@56370
   552
lp15@62534
   553
lemma deriv_cmult [simp]:
lp15@62534
   554
  "f field_differentiable at z \<Longrightarrow> deriv (\<lambda>w. c * f w) z = c * deriv f z"
lp15@62534
   555
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   556
  by (auto intro!: DERIV_imp_deriv derivative_eq_intros)
hoelzl@56370
   557
lp15@62534
   558
lemma deriv_cmult_right [simp]:
lp15@62534
   559
  "f field_differentiable at z \<Longrightarrow> deriv (\<lambda>w. f w * c) z = deriv f z * c"
lp15@62534
   560
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   561
  by (auto intro!: DERIV_imp_deriv derivative_eq_intros)
hoelzl@56370
   562
lp15@62534
   563
lemma deriv_cdivide_right [simp]:
lp15@62534
   564
  "f field_differentiable at z \<Longrightarrow> deriv (\<lambda>w. f w / c) z = deriv f z / c"
lp15@62217
   565
  unfolding Fields.field_class.field_divide_inverse
lp15@62534
   566
  by (blast intro: deriv_cmult_right)
lp15@62217
   567
hoelzl@56370
   568
lemma complex_derivative_transform_within_open:
lp15@61609
   569
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s; open s; z \<in> s; \<And>w. w \<in> s \<Longrightarrow> f w = g w\<rbrakk>
hoelzl@56370
   570
   \<Longrightarrow> deriv f z = deriv g z"
hoelzl@56370
   571
  unfolding holomorphic_on_def
hoelzl@56370
   572
  by (rule DERIV_imp_deriv)
lp15@62534
   573
     (metis DERIV_deriv_iff_field_differentiable DERIV_transform_within_open at_within_open)
hoelzl@56370
   574
lp15@62534
   575
lemma deriv_compose_linear:
lp15@62534
   576
  "f field_differentiable at (c * z) \<Longrightarrow> deriv (\<lambda>w. f (c * w)) z = c * deriv f (c * z)"
hoelzl@56370
   577
apply (rule DERIV_imp_deriv)
lp15@62534
   578
apply (simp add: DERIV_deriv_iff_field_differentiable [symmetric])
haftmann@59554
   579
apply (drule DERIV_chain' [of "times c" c z UNIV f "deriv f (c * z)", OF DERIV_cmult_Id])
haftmann@59554
   580
apply (simp add: algebra_simps)
hoelzl@56370
   581
done
hoelzl@56370
   582
lp15@62533
   583
lemma nonzero_deriv_nonconstant:
lp15@62533
   584
  assumes df: "DERIV f \<xi> :> df" and S: "open S" "\<xi> \<in> S" and "df \<noteq> 0"
lp15@62533
   585
    shows "\<not> f constant_on S"
lp15@62533
   586
unfolding constant_on_def
lp15@62533
   587
by (metis \<open>df \<noteq> 0\<close> DERIV_transform_within_open [OF df S] DERIV_const DERIV_unique)
lp15@62533
   588
lp15@62533
   589
lemma holomorphic_nonconstant:
lp15@62533
   590
  assumes holf: "f holomorphic_on S" and "open S" "\<xi> \<in> S" "deriv f \<xi> \<noteq> 0"
lp15@62533
   591
    shows "\<not> f constant_on S"
lp15@62533
   592
    apply (rule nonzero_deriv_nonconstant [of f "deriv f \<xi>" \<xi> S])
lp15@62533
   593
    using assms
lp15@62533
   594
    apply (auto simp: holomorphic_derivI)
lp15@62533
   595
    done
lp15@62533
   596
wenzelm@60420
   597
subsection\<open>Analyticity on a set\<close>
lp15@56215
   598
lp15@61609
   599
definition analytic_on (infixl "(analytic'_on)" 50)
lp15@56215
   600
  where
lp15@56215
   601
   "f analytic_on s \<equiv> \<forall>x \<in> s. \<exists>e. 0 < e \<and> f holomorphic_on (ball x e)"
lp15@56215
   602
hoelzl@56370
   603
lemma analytic_imp_holomorphic: "f analytic_on s \<Longrightarrow> f holomorphic_on s"
hoelzl@56370
   604
  by (simp add: at_within_open [OF _ open_ball] analytic_on_def holomorphic_on_def)
lp15@62534
   605
     (metis centre_in_ball field_differentiable_at_within)
lp15@56215
   606
hoelzl@56370
   607
lemma analytic_on_open: "open s \<Longrightarrow> f analytic_on s \<longleftrightarrow> f holomorphic_on s"
lp15@56215
   608
apply (auto simp: analytic_imp_holomorphic)
lp15@56215
   609
apply (auto simp: analytic_on_def holomorphic_on_def)
lp15@56215
   610
by (metis holomorphic_on_def holomorphic_on_subset open_contains_ball)
lp15@56215
   611
lp15@56215
   612
lemma analytic_on_imp_differentiable_at:
lp15@62534
   613
  "f analytic_on s \<Longrightarrow> x \<in> s \<Longrightarrow> f field_differentiable (at x)"
hoelzl@56370
   614
 apply (auto simp: analytic_on_def holomorphic_on_def)
lp15@62534
   615
by (metis Topology_Euclidean_Space.open_ball centre_in_ball field_differentiable_within_open)
lp15@56215
   616
hoelzl@56370
   617
lemma analytic_on_subset: "f analytic_on s \<Longrightarrow> t \<subseteq> s \<Longrightarrow> f analytic_on t"
lp15@56215
   618
  by (auto simp: analytic_on_def)
lp15@56215
   619
hoelzl@56370
   620
lemma analytic_on_Un: "f analytic_on (s \<union> t) \<longleftrightarrow> f analytic_on s \<and> f analytic_on t"
lp15@56215
   621
  by (auto simp: analytic_on_def)
lp15@56215
   622
wenzelm@60585
   623
lemma analytic_on_Union: "f analytic_on (\<Union>s) \<longleftrightarrow> (\<forall>t \<in> s. f analytic_on t)"
hoelzl@56370
   624
  by (auto simp: analytic_on_def)
hoelzl@56370
   625
hoelzl@56370
   626
lemma analytic_on_UN: "f analytic_on (\<Union>i\<in>I. s i) \<longleftrightarrow> (\<forall>i\<in>I. f analytic_on (s i))"
lp15@56215
   627
  by (auto simp: analytic_on_def)
lp15@61609
   628
lp15@56215
   629
lemma analytic_on_holomorphic:
lp15@56215
   630
  "f analytic_on s \<longleftrightarrow> (\<exists>t. open t \<and> s \<subseteq> t \<and> f holomorphic_on t)"
lp15@56215
   631
  (is "?lhs = ?rhs")
lp15@56215
   632
proof -
lp15@56215
   633
  have "?lhs \<longleftrightarrow> (\<exists>t. open t \<and> s \<subseteq> t \<and> f analytic_on t)"
lp15@56215
   634
  proof safe
lp15@56215
   635
    assume "f analytic_on s"
lp15@56215
   636
    then show "\<exists>t. open t \<and> s \<subseteq> t \<and> f analytic_on t"
lp15@56215
   637
      apply (simp add: analytic_on_def)
lp15@56215
   638
      apply (rule exI [where x="\<Union>{u. open u \<and> f analytic_on u}"], auto)
lp15@56215
   639
      apply (metis Topology_Euclidean_Space.open_ball analytic_on_open centre_in_ball)
lp15@56215
   640
      by (metis analytic_on_def)
lp15@56215
   641
  next
lp15@56215
   642
    fix t
lp15@61609
   643
    assume "open t" "s \<subseteq> t" "f analytic_on t"
lp15@56215
   644
    then show "f analytic_on s"
lp15@56215
   645
        by (metis analytic_on_subset)
lp15@56215
   646
  qed
lp15@56215
   647
  also have "... \<longleftrightarrow> ?rhs"
lp15@56215
   648
    by (auto simp: analytic_on_open)
lp15@56215
   649
  finally show ?thesis .
lp15@56215
   650
qed
lp15@56215
   651
lp15@56215
   652
lemma analytic_on_linear: "(op * c) analytic_on s"
hoelzl@56370
   653
  by (auto simp add: analytic_on_holomorphic holomorphic_on_linear)
lp15@56215
   654
lp15@56215
   655
lemma analytic_on_const: "(\<lambda>z. c) analytic_on s"
hoelzl@56370
   656
  by (metis analytic_on_def holomorphic_on_const zero_less_one)
hoelzl@56370
   657
hoelzl@56370
   658
lemma analytic_on_ident: "(\<lambda>x. x) analytic_on s"
hoelzl@56370
   659
  by (simp add: analytic_on_def holomorphic_on_ident gt_ex)
lp15@56215
   660
lp15@56215
   661
lemma analytic_on_id: "id analytic_on s"
hoelzl@56370
   662
  unfolding id_def by (rule analytic_on_ident)
lp15@56215
   663
lp15@56215
   664
lemma analytic_on_compose:
lp15@56215
   665
  assumes f: "f analytic_on s"
lp15@56215
   666
      and g: "g analytic_on (f ` s)"
lp15@56215
   667
    shows "(g o f) analytic_on s"
lp15@56215
   668
unfolding analytic_on_def
lp15@56215
   669
proof (intro ballI)
lp15@56215
   670
  fix x
lp15@56215
   671
  assume x: "x \<in> s"
lp15@56215
   672
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball x e" using f
lp15@56215
   673
    by (metis analytic_on_def)
lp15@56215
   674
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball (f x) e'" using g
lp15@61609
   675
    by (metis analytic_on_def g image_eqI x)
lp15@56215
   676
  have "isCont f x"
lp15@62534
   677
    by (metis analytic_on_imp_differentiable_at field_differentiable_imp_continuous_at f x)
lp15@56215
   678
  with e' obtain d where d: "0 < d" and fd: "f ` ball x d \<subseteq> ball (f x) e'"
lp15@56215
   679
     by (auto simp: continuous_at_ball)
lp15@61609
   680
  have "g \<circ> f holomorphic_on ball x (min d e)"
lp15@56215
   681
    apply (rule holomorphic_on_compose)
lp15@56215
   682
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   683
    by (metis fd gh holomorphic_on_subset image_mono min.cobounded1 subset_ball)
lp15@56215
   684
  then show "\<exists>e>0. g \<circ> f holomorphic_on ball x e"
lp15@61609
   685
    by (metis d e min_less_iff_conj)
lp15@56215
   686
qed
lp15@56215
   687
lp15@56215
   688
lemma analytic_on_compose_gen:
lp15@56215
   689
  "f analytic_on s \<Longrightarrow> g analytic_on t \<Longrightarrow> (\<And>z. z \<in> s \<Longrightarrow> f z \<in> t)
lp15@56215
   690
             \<Longrightarrow> g o f analytic_on s"
lp15@56215
   691
by (metis analytic_on_compose analytic_on_subset image_subset_iff)
lp15@56215
   692
lp15@56215
   693
lemma analytic_on_neg:
lp15@56215
   694
  "f analytic_on s \<Longrightarrow> (\<lambda>z. -(f z)) analytic_on s"
lp15@56215
   695
by (metis analytic_on_holomorphic holomorphic_on_minus)
lp15@56215
   696
lp15@56215
   697
lemma analytic_on_add:
lp15@56215
   698
  assumes f: "f analytic_on s"
lp15@56215
   699
      and g: "g analytic_on s"
lp15@56215
   700
    shows "(\<lambda>z. f z + g z) analytic_on s"
lp15@56215
   701
unfolding analytic_on_def
lp15@56215
   702
proof (intro ballI)
lp15@56215
   703
  fix z
lp15@56215
   704
  assume z: "z \<in> s"
lp15@56215
   705
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   706
    by (metis analytic_on_def)
lp15@56215
   707
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball z e'" using g
lp15@61609
   708
    by (metis analytic_on_def g z)
lp15@61609
   709
  have "(\<lambda>z. f z + g z) holomorphic_on ball z (min e e')"
lp15@61609
   710
    apply (rule holomorphic_on_add)
lp15@56215
   711
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   712
    by (metis gh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   713
  then show "\<exists>e>0. (\<lambda>z. f z + g z) holomorphic_on ball z e"
lp15@56215
   714
    by (metis e e' min_less_iff_conj)
lp15@56215
   715
qed
lp15@56215
   716
lp15@56215
   717
lemma analytic_on_diff:
lp15@56215
   718
  assumes f: "f analytic_on s"
lp15@56215
   719
      and g: "g analytic_on s"
lp15@56215
   720
    shows "(\<lambda>z. f z - g z) analytic_on s"
lp15@56215
   721
unfolding analytic_on_def
lp15@56215
   722
proof (intro ballI)
lp15@56215
   723
  fix z
lp15@56215
   724
  assume z: "z \<in> s"
lp15@56215
   725
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   726
    by (metis analytic_on_def)
lp15@56215
   727
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball z e'" using g
lp15@61609
   728
    by (metis analytic_on_def g z)
lp15@61609
   729
  have "(\<lambda>z. f z - g z) holomorphic_on ball z (min e e')"
lp15@61609
   730
    apply (rule holomorphic_on_diff)
lp15@56215
   731
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   732
    by (metis gh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   733
  then show "\<exists>e>0. (\<lambda>z. f z - g z) holomorphic_on ball z e"
lp15@56215
   734
    by (metis e e' min_less_iff_conj)
lp15@56215
   735
qed
lp15@56215
   736
lp15@56215
   737
lemma analytic_on_mult:
lp15@56215
   738
  assumes f: "f analytic_on s"
lp15@56215
   739
      and g: "g analytic_on s"
lp15@56215
   740
    shows "(\<lambda>z. f z * g z) analytic_on s"
lp15@56215
   741
unfolding analytic_on_def
lp15@56215
   742
proof (intro ballI)
lp15@56215
   743
  fix z
lp15@56215
   744
  assume z: "z \<in> s"
lp15@56215
   745
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   746
    by (metis analytic_on_def)
lp15@56215
   747
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball z e'" using g
lp15@61609
   748
    by (metis analytic_on_def g z)
lp15@61609
   749
  have "(\<lambda>z. f z * g z) holomorphic_on ball z (min e e')"
lp15@61609
   750
    apply (rule holomorphic_on_mult)
lp15@56215
   751
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   752
    by (metis gh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   753
  then show "\<exists>e>0. (\<lambda>z. f z * g z) holomorphic_on ball z e"
lp15@56215
   754
    by (metis e e' min_less_iff_conj)
lp15@56215
   755
qed
lp15@56215
   756
lp15@56215
   757
lemma analytic_on_inverse:
lp15@56215
   758
  assumes f: "f analytic_on s"
lp15@56215
   759
      and nz: "(\<And>z. z \<in> s \<Longrightarrow> f z \<noteq> 0)"
lp15@56215
   760
    shows "(\<lambda>z. inverse (f z)) analytic_on s"
lp15@56215
   761
unfolding analytic_on_def
lp15@56215
   762
proof (intro ballI)
lp15@56215
   763
  fix z
lp15@56215
   764
  assume z: "z \<in> s"
lp15@56215
   765
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   766
    by (metis analytic_on_def)
lp15@56215
   767
  have "continuous_on (ball z e) f"
lp15@56215
   768
    by (metis fh holomorphic_on_imp_continuous_on)
lp15@61609
   769
  then obtain e' where e': "0 < e'" and nz': "\<And>y. dist z y < e' \<Longrightarrow> f y \<noteq> 0"
lp15@61609
   770
    by (metis Topology_Euclidean_Space.open_ball centre_in_ball continuous_on_open_avoid e z nz)
lp15@61609
   771
  have "(\<lambda>z. inverse (f z)) holomorphic_on ball z (min e e')"
lp15@56215
   772
    apply (rule holomorphic_on_inverse)
lp15@56215
   773
    apply (metis fh holomorphic_on_subset min.cobounded2 min.commute subset_ball)
lp15@61609
   774
    by (metis nz' mem_ball min_less_iff_conj)
lp15@56215
   775
  then show "\<exists>e>0. (\<lambda>z. inverse (f z)) holomorphic_on ball z e"
lp15@56215
   776
    by (metis e e' min_less_iff_conj)
lp15@56215
   777
qed
lp15@56215
   778
lp15@56215
   779
lemma analytic_on_divide:
lp15@56215
   780
  assumes f: "f analytic_on s"
lp15@56215
   781
      and g: "g analytic_on s"
lp15@56215
   782
      and nz: "(\<And>z. z \<in> s \<Longrightarrow> g z \<noteq> 0)"
lp15@56215
   783
    shows "(\<lambda>z. f z / g z) analytic_on s"
lp15@56215
   784
unfolding divide_inverse
lp15@56215
   785
by (metis analytic_on_inverse analytic_on_mult f g nz)
lp15@56215
   786
lp15@56215
   787
lemma analytic_on_power:
lp15@56215
   788
  "f analytic_on s \<Longrightarrow> (\<lambda>z. (f z) ^ n) analytic_on s"
lp15@56215
   789
by (induct n) (auto simp: analytic_on_const analytic_on_mult)
lp15@56215
   790
lp15@56215
   791
lemma analytic_on_setsum:
hoelzl@56369
   792
  "(\<And>i. i \<in> I \<Longrightarrow> (f i) analytic_on s) \<Longrightarrow> (\<lambda>x. setsum (\<lambda>i. f i x) I) analytic_on s"
hoelzl@56369
   793
  by (induct I rule: infinite_finite_induct) (auto simp: analytic_on_const analytic_on_add)
lp15@56215
   794
lp15@62408
   795
lemma deriv_left_inverse:
lp15@62408
   796
  assumes "f holomorphic_on S" and "g holomorphic_on T"
lp15@62408
   797
      and "open S" and "open T"
lp15@62408
   798
      and "f ` S \<subseteq> T"
lp15@62408
   799
      and [simp]: "\<And>z. z \<in> S \<Longrightarrow> g (f z) = z"
lp15@62408
   800
      and "w \<in> S"
lp15@62408
   801
    shows "deriv f w * deriv g (f w) = 1"
lp15@62408
   802
proof -
lp15@62408
   803
  have "deriv f w * deriv g (f w) = deriv g (f w) * deriv f w"
lp15@62408
   804
    by (simp add: algebra_simps)
lp15@62408
   805
  also have "... = deriv (g o f) w"
lp15@62408
   806
    using assms
lp15@62408
   807
    by (metis analytic_on_imp_differentiable_at analytic_on_open complex_derivative_chain image_subset_iff)
lp15@62408
   808
  also have "... = deriv id w"
lp15@62408
   809
    apply (rule complex_derivative_transform_within_open [where s=S])
lp15@62408
   810
    apply (rule assms holomorphic_on_compose_gen holomorphic_intros)+
lp15@62408
   811
    apply simp
lp15@62408
   812
    done
lp15@62408
   813
  also have "... = 1"
lp15@62408
   814
    by simp
lp15@62408
   815
  finally show ?thesis .
lp15@62408
   816
qed
lp15@62408
   817
lp15@62408
   818
subsection\<open>analyticity at a point\<close>
lp15@56215
   819
lp15@56215
   820
lemma analytic_at_ball:
lp15@56215
   821
  "f analytic_on {z} \<longleftrightarrow> (\<exists>e. 0<e \<and> f holomorphic_on ball z e)"
lp15@56215
   822
by (metis analytic_on_def singleton_iff)
lp15@56215
   823
lp15@56215
   824
lemma analytic_at:
lp15@56215
   825
    "f analytic_on {z} \<longleftrightarrow> (\<exists>s. open s \<and> z \<in> s \<and> f holomorphic_on s)"
lp15@56215
   826
by (metis analytic_on_holomorphic empty_subsetI insert_subset)
lp15@56215
   827
lp15@56215
   828
lemma analytic_on_analytic_at:
lp15@56215
   829
    "f analytic_on s \<longleftrightarrow> (\<forall>z \<in> s. f analytic_on {z})"
lp15@56215
   830
by (metis analytic_at_ball analytic_on_def)
lp15@56215
   831
lp15@56215
   832
lemma analytic_at_two:
lp15@56215
   833
  "f analytic_on {z} \<and> g analytic_on {z} \<longleftrightarrow>
lp15@56215
   834
   (\<exists>s. open s \<and> z \<in> s \<and> f holomorphic_on s \<and> g holomorphic_on s)"
lp15@56215
   835
  (is "?lhs = ?rhs")
lp15@61609
   836
proof
lp15@56215
   837
  assume ?lhs
lp15@61609
   838
  then obtain s t
lp15@56215
   839
    where st: "open s" "z \<in> s" "f holomorphic_on s"
lp15@56215
   840
              "open t" "z \<in> t" "g holomorphic_on t"
lp15@56215
   841
    by (auto simp: analytic_at)
lp15@56215
   842
  show ?rhs
lp15@56215
   843
    apply (rule_tac x="s \<inter> t" in exI)
lp15@56215
   844
    using st
lp15@56215
   845
    apply (auto simp: Diff_subset holomorphic_on_subset)
lp15@56215
   846
    done
lp15@56215
   847
next
lp15@61609
   848
  assume ?rhs
lp15@56215
   849
  then show ?lhs
lp15@56215
   850
    by (force simp add: analytic_at)
lp15@56215
   851
qed
lp15@56215
   852
wenzelm@60420
   853
subsection\<open>Combining theorems for derivative with ``analytic at'' hypotheses\<close>
lp15@56215
   854
lp15@61609
   855
lemma
lp15@56215
   856
  assumes "f analytic_on {z}" "g analytic_on {z}"
hoelzl@56370
   857
  shows complex_derivative_add_at: "deriv (\<lambda>w. f w + g w) z = deriv f z + deriv g z"
hoelzl@56370
   858
    and complex_derivative_diff_at: "deriv (\<lambda>w. f w - g w) z = deriv f z - deriv g z"
hoelzl@56370
   859
    and complex_derivative_mult_at: "deriv (\<lambda>w. f w * g w) z =
hoelzl@56370
   860
           f z * deriv g z + deriv f z * g z"
lp15@56215
   861
proof -
lp15@56215
   862
  obtain s where s: "open s" "z \<in> s" "f holomorphic_on s" "g holomorphic_on s"
lp15@56215
   863
    using assms by (metis analytic_at_two)
hoelzl@56370
   864
  show "deriv (\<lambda>w. f w + g w) z = deriv f z + deriv g z"
hoelzl@56370
   865
    apply (rule DERIV_imp_deriv [OF DERIV_add])
lp15@56215
   866
    using s
lp15@62534
   867
    apply (auto simp: holomorphic_on_open field_differentiable_def DERIV_deriv_iff_field_differentiable)
lp15@56215
   868
    done
hoelzl@56370
   869
  show "deriv (\<lambda>w. f w - g w) z = deriv f z - deriv g z"
hoelzl@56370
   870
    apply (rule DERIV_imp_deriv [OF DERIV_diff])
lp15@56215
   871
    using s
lp15@62534
   872
    apply (auto simp: holomorphic_on_open field_differentiable_def DERIV_deriv_iff_field_differentiable)
lp15@56215
   873
    done
hoelzl@56370
   874
  show "deriv (\<lambda>w. f w * g w) z = f z * deriv g z + deriv f z * g z"
hoelzl@56370
   875
    apply (rule DERIV_imp_deriv [OF DERIV_mult'])
lp15@56215
   876
    using s
lp15@62534
   877
    apply (auto simp: holomorphic_on_open field_differentiable_def DERIV_deriv_iff_field_differentiable)
lp15@56215
   878
    done
lp15@56215
   879
qed
lp15@56215
   880
lp15@62534
   881
lemma deriv_cmult_at:
hoelzl@56370
   882
  "f analytic_on {z} \<Longrightarrow>  deriv (\<lambda>w. c * f w) z = c * deriv f z"
lp15@61848
   883
by (auto simp: complex_derivative_mult_at deriv_const analytic_on_const)
lp15@56215
   884
lp15@62534
   885
lemma deriv_cmult_right_at:
hoelzl@56370
   886
  "f analytic_on {z} \<Longrightarrow>  deriv (\<lambda>w. f w * c) z = deriv f z * c"
lp15@61848
   887
by (auto simp: complex_derivative_mult_at deriv_const analytic_on_const)
lp15@56215
   888
wenzelm@60420
   889
subsection\<open>Complex differentiation of sequences and series\<close>
lp15@56215
   890
eberlm@61531
   891
(* TODO: Could probably be simplified using Uniform_Limit *)
lp15@56215
   892
lemma has_complex_derivative_sequence:
lp15@56215
   893
  fixes s :: "complex set"
lp15@56215
   894
  assumes cvs: "convex s"
lp15@56215
   895
      and df:  "\<And>n x. x \<in> s \<Longrightarrow> (f n has_field_derivative f' n x) (at x within s)"
lp15@56215
   896
      and conv: "\<And>e. 0 < e \<Longrightarrow> \<exists>N. \<forall>n x. n \<ge> N \<longrightarrow> x \<in> s \<longrightarrow> norm (f' n x - g' x) \<le> e"
wenzelm@61973
   897
      and "\<exists>x l. x \<in> s \<and> ((\<lambda>n. f n x) \<longlongrightarrow> l) sequentially"
wenzelm@61973
   898
    shows "\<exists>g. \<forall>x \<in> s. ((\<lambda>n. f n x) \<longlongrightarrow> g x) sequentially \<and>
lp15@56215
   899
                       (g has_field_derivative (g' x)) (at x within s)"
lp15@56215
   900
proof -
wenzelm@61973
   901
  from assms obtain x l where x: "x \<in> s" and tf: "((\<lambda>n. f n x) \<longlongrightarrow> l) sequentially"
lp15@56215
   902
    by blast
lp15@56215
   903
  { fix e::real assume e: "e > 0"
lp15@56215
   904
    then obtain N where N: "\<forall>n\<ge>N. \<forall>x. x \<in> s \<longrightarrow> cmod (f' n x - g' x) \<le> e"
lp15@61609
   905
      by (metis conv)
lp15@56215
   906
    have "\<exists>N. \<forall>n\<ge>N. \<forall>x\<in>s. \<forall>h. cmod (f' n x * h - g' x * h) \<le> e * cmod h"
lp15@56215
   907
    proof (rule exI [of _ N], clarify)
lp15@56215
   908
      fix n y h
lp15@56215
   909
      assume "N \<le> n" "y \<in> s"
lp15@56215
   910
      then have "cmod (f' n y - g' y) \<le> e"
lp15@56215
   911
        by (metis N)
lp15@56215
   912
      then have "cmod h * cmod (f' n y - g' y) \<le> cmod h * e"
lp15@56215
   913
        by (auto simp: antisym_conv2 mult_le_cancel_left norm_triangle_ineq2)
lp15@56215
   914
      then show "cmod (f' n y * h - g' y * h) \<le> e * cmod h"
lp15@56215
   915
        by (simp add: norm_mult [symmetric] field_simps)
lp15@56215
   916
    qed
lp15@56215
   917
  } note ** = this
lp15@56215
   918
  show ?thesis
lp15@56215
   919
  unfolding has_field_derivative_def
lp15@56215
   920
  proof (rule has_derivative_sequence [OF cvs _ _ x])
lp15@56215
   921
    show "\<forall>n. \<forall>x\<in>s. (f n has_derivative (op * (f' n x))) (at x within s)"
lp15@56215
   922
      by (metis has_field_derivative_def df)
wenzelm@61969
   923
  next show "(\<lambda>n. f n x) \<longlonglongrightarrow> l"
lp15@56215
   924
    by (rule tf)
lp15@56215
   925
  next show "\<forall>e>0. \<exists>N. \<forall>n\<ge>N. \<forall>x\<in>s. \<forall>h. cmod (f' n x * h - g' x * h) \<le> e * cmod h"
lp15@56215
   926
    by (blast intro: **)
lp15@56215
   927
  qed
lp15@56215
   928
qed
lp15@56215
   929
lp15@56215
   930
lemma has_complex_derivative_series:
lp15@56215
   931
  fixes s :: "complex set"
lp15@56215
   932
  assumes cvs: "convex s"
lp15@56215
   933
      and df:  "\<And>n x. x \<in> s \<Longrightarrow> (f n has_field_derivative f' n x) (at x within s)"
lp15@61609
   934
      and conv: "\<And>e. 0 < e \<Longrightarrow> \<exists>N. \<forall>n x. n \<ge> N \<longrightarrow> x \<in> s
lp15@56215
   935
                \<longrightarrow> cmod ((\<Sum>i<n. f' i x) - g' x) \<le> e"
lp15@56215
   936
      and "\<exists>x l. x \<in> s \<and> ((\<lambda>n. f n x) sums l)"
lp15@56215
   937
    shows "\<exists>g. \<forall>x \<in> s. ((\<lambda>n. f n x) sums g x) \<and> ((g has_field_derivative g' x) (at x within s))"
lp15@56215
   938
proof -
lp15@56215
   939
  from assms obtain x l where x: "x \<in> s" and sf: "((\<lambda>n. f n x) sums l)"
lp15@56215
   940
    by blast
lp15@56215
   941
  { fix e::real assume e: "e > 0"
lp15@61609
   942
    then obtain N where N: "\<forall>n x. n \<ge> N \<longrightarrow> x \<in> s
lp15@56215
   943
            \<longrightarrow> cmod ((\<Sum>i<n. f' i x) - g' x) \<le> e"
lp15@61609
   944
      by (metis conv)
lp15@56215
   945
    have "\<exists>N. \<forall>n\<ge>N. \<forall>x\<in>s. \<forall>h. cmod ((\<Sum>i<n. h * f' i x) - g' x * h) \<le> e * cmod h"
lp15@56215
   946
    proof (rule exI [of _ N], clarify)
lp15@56215
   947
      fix n y h
lp15@56215
   948
      assume "N \<le> n" "y \<in> s"
lp15@56215
   949
      then have "cmod ((\<Sum>i<n. f' i y) - g' y) \<le> e"
lp15@56215
   950
        by (metis N)
lp15@56215
   951
      then have "cmod h * cmod ((\<Sum>i<n. f' i y) - g' y) \<le> cmod h * e"
lp15@56215
   952
        by (auto simp: antisym_conv2 mult_le_cancel_left norm_triangle_ineq2)
lp15@56215
   953
      then show "cmod ((\<Sum>i<n. h * f' i y) - g' y * h) \<le> e * cmod h"
lp15@56215
   954
        by (simp add: norm_mult [symmetric] field_simps setsum_right_distrib)
lp15@56215
   955
    qed
lp15@56215
   956
  } note ** = this
lp15@56215
   957
  show ?thesis
lp15@56215
   958
  unfolding has_field_derivative_def
lp15@56215
   959
  proof (rule has_derivative_series [OF cvs _ _ x])
lp15@56215
   960
    fix n x
lp15@56215
   961
    assume "x \<in> s"
lp15@56215
   962
    then show "((f n) has_derivative (\<lambda>z. z * f' n x)) (at x within s)"
lp15@56215
   963
      by (metis df has_field_derivative_def mult_commute_abs)
lp15@56215
   964
  next show " ((\<lambda>n. f n x) sums l)"
lp15@56215
   965
    by (rule sf)
lp15@56215
   966
  next show "\<forall>e>0. \<exists>N. \<forall>n\<ge>N. \<forall>x\<in>s. \<forall>h. cmod ((\<Sum>i<n. h * f' i x) - g' x * h) \<le> e * cmod h"
lp15@56215
   967
    by (blast intro: **)
lp15@56215
   968
  qed
lp15@56215
   969
qed
lp15@56215
   970
eberlm@61531
   971
lp15@62534
   972
lemma field_differentiable_series:
eberlm@61531
   973
  fixes f :: "nat \<Rightarrow> complex \<Rightarrow> complex"
eberlm@61531
   974
  assumes "convex s" "open s"
eberlm@61531
   975
  assumes "\<And>n x. x \<in> s \<Longrightarrow> (f n has_field_derivative f' n x) (at x)"
eberlm@61531
   976
  assumes "uniformly_convergent_on s (\<lambda>n x. \<Sum>i<n. f' i x)"
eberlm@61531
   977
  assumes "x0 \<in> s" "summable (\<lambda>n. f n x0)" and x: "x \<in> s"
lp15@62534
   978
  shows   "summable (\<lambda>n. f n x)" and "(\<lambda>x. \<Sum>n. f n x) field_differentiable (at x)"
eberlm@61531
   979
proof -
eberlm@61531
   980
  from assms(4) obtain g' where A: "uniform_limit s (\<lambda>n x. \<Sum>i<n. f' i x) g' sequentially"
eberlm@61531
   981
    unfolding uniformly_convergent_on_def by blast
wenzelm@61808
   982
  from x and \<open>open s\<close> have s: "at x within s = at x" by (rule at_within_open)
eberlm@61531
   983
  have "\<exists>g. \<forall>x\<in>s. (\<lambda>n. f n x) sums g x \<and> (g has_field_derivative g' x) (at x within s)"
eberlm@61531
   984
    by (intro has_field_derivative_series[of s f f' g' x0] assms A has_field_derivative_at_within)
eberlm@61531
   985
  then obtain g where g: "\<And>x. x \<in> s \<Longrightarrow> (\<lambda>n. f n x) sums g x"
eberlm@61531
   986
    "\<And>x. x \<in> s \<Longrightarrow> (g has_field_derivative g' x) (at x within s)" by blast
eberlm@61531
   987
  from g[OF x] show "summable (\<lambda>n. f n x)" by (auto simp: summable_def)
eberlm@61531
   988
  from g(2)[OF x] have g': "(g has_derivative op * (g' x)) (at x)"
eberlm@61531
   989
    by (simp add: has_field_derivative_def s)
eberlm@61531
   990
  have "((\<lambda>x. \<Sum>n. f n x) has_derivative op * (g' x)) (at x)"
paulson@62087
   991
    by (rule has_derivative_transform_within_open[OF g' \<open>open s\<close> x])
eberlm@61531
   992
       (insert g, auto simp: sums_iff)
lp15@62534
   993
  thus "(\<lambda>x. \<Sum>n. f n x) field_differentiable (at x)" unfolding differentiable_def
lp15@62534
   994
    by (auto simp: summable_def field_differentiable_def has_field_derivative_def)
eberlm@61531
   995
qed
eberlm@61531
   996
lp15@62534
   997
lemma field_differentiable_series':
eberlm@61531
   998
  fixes f :: "nat \<Rightarrow> complex \<Rightarrow> complex"
eberlm@61531
   999
  assumes "convex s" "open s"
eberlm@61531
  1000
  assumes "\<And>n x. x \<in> s \<Longrightarrow> (f n has_field_derivative f' n x) (at x)"
eberlm@61531
  1001
  assumes "uniformly_convergent_on s (\<lambda>n x. \<Sum>i<n. f' i x)"
eberlm@61531
  1002
  assumes "x0 \<in> s" "summable (\<lambda>n. f n x0)"
lp15@62534
  1003
  shows   "(\<lambda>x. \<Sum>n. f n x) field_differentiable (at x0)"
lp15@62534
  1004
  using field_differentiable_series[OF assms, of x0] \<open>x0 \<in> s\<close> by blast+
eberlm@61531
  1005
wenzelm@60420
  1006
subsection\<open>Bound theorem\<close>
lp15@56215
  1007
lp15@62534
  1008
lemma field_differentiable_bound:
lp15@56215
  1009
  fixes s :: "complex set"
lp15@56215
  1010
  assumes cvs: "convex s"
lp15@56215
  1011
      and df:  "\<And>z. z \<in> s \<Longrightarrow> (f has_field_derivative f' z) (at z within s)"
lp15@56215
  1012
      and dn:  "\<And>z. z \<in> s \<Longrightarrow> norm (f' z) \<le> B"
lp15@56215
  1013
      and "x \<in> s"  "y \<in> s"
lp15@56215
  1014
    shows "norm(f x - f y) \<le> B * norm(x - y)"
lp15@56215
  1015
  apply (rule differentiable_bound [OF cvs])
huffman@56223
  1016
  apply (rule ballI, erule df [unfolded has_field_derivative_def])
huffman@56223
  1017
  apply (rule ballI, rule onorm_le, simp add: norm_mult mult_right_mono dn)
huffman@56223
  1018
  apply fact
huffman@56223
  1019
  apply fact
lp15@56215
  1020
  done
lp15@56215
  1021
lp15@62408
  1022
subsection\<open>Inverse function theorem for complex derivatives\<close>
lp15@56215
  1023
lp15@56215
  1024
lemma has_complex_derivative_inverse_basic:
lp15@56215
  1025
  fixes f :: "complex \<Rightarrow> complex"
lp15@56215
  1026
  shows "DERIV f (g y) :> f' \<Longrightarrow>
lp15@56215
  1027
        f' \<noteq> 0 \<Longrightarrow>
lp15@56215
  1028
        continuous (at y) g \<Longrightarrow>
lp15@56215
  1029
        open t \<Longrightarrow>
lp15@56215
  1030
        y \<in> t \<Longrightarrow>
lp15@56215
  1031
        (\<And>z. z \<in> t \<Longrightarrow> f (g z) = z)
lp15@56215
  1032
        \<Longrightarrow> DERIV g y :> inverse (f')"
lp15@56215
  1033
  unfolding has_field_derivative_def
lp15@56215
  1034
  apply (rule has_derivative_inverse_basic)
lp15@56215
  1035
  apply (auto simp:  bounded_linear_mult_right)
lp15@56215
  1036
  done
lp15@56215
  1037
lp15@56215
  1038
(*Used only once, in Multivariate/cauchy.ml. *)
lp15@56215
  1039
lemma has_complex_derivative_inverse_strong:
lp15@56215
  1040
  fixes f :: "complex \<Rightarrow> complex"
lp15@56215
  1041
  shows "DERIV f x :> f' \<Longrightarrow>
lp15@56215
  1042
         f' \<noteq> 0 \<Longrightarrow>
lp15@56215
  1043
         open s \<Longrightarrow>
lp15@56215
  1044
         x \<in> s \<Longrightarrow>
lp15@56215
  1045
         continuous_on s f \<Longrightarrow>
lp15@56215
  1046
         (\<And>z. z \<in> s \<Longrightarrow> g (f z) = z)
lp15@56215
  1047
         \<Longrightarrow> DERIV g (f x) :> inverse (f')"
lp15@56215
  1048
  unfolding has_field_derivative_def
lp15@56215
  1049
  apply (rule has_derivative_inverse_strong [of s x f g ])
lp15@61609
  1050
  using assms
lp15@56215
  1051
  by auto
lp15@56215
  1052
lp15@56215
  1053
lemma has_complex_derivative_inverse_strong_x:
lp15@56215
  1054
  fixes f :: "complex \<Rightarrow> complex"
lp15@56215
  1055
  shows  "DERIV f (g y) :> f' \<Longrightarrow>
lp15@56215
  1056
          f' \<noteq> 0 \<Longrightarrow>
lp15@56215
  1057
          open s \<Longrightarrow>
lp15@56215
  1058
          continuous_on s f \<Longrightarrow>
lp15@56215
  1059
          g y \<in> s \<Longrightarrow> f(g y) = y \<Longrightarrow>
lp15@56215
  1060
          (\<And>z. z \<in> s \<Longrightarrow> g (f z) = z)
lp15@56215
  1061
          \<Longrightarrow> DERIV g y :> inverse (f')"
lp15@56215
  1062
  unfolding has_field_derivative_def
lp15@56215
  1063
  apply (rule has_derivative_inverse_strong_x [of s g y f])
lp15@61609
  1064
  using assms
lp15@56215
  1065
  by auto
lp15@56215
  1066
wenzelm@60420
  1067
subsection \<open>Taylor on Complex Numbers\<close>
lp15@56215
  1068
lp15@56215
  1069
lemma setsum_Suc_reindex:
lp15@56215
  1070
  fixes f :: "nat \<Rightarrow> 'a::ab_group_add"
lp15@56215
  1071
    shows  "setsum f {0..n} = f 0 - f (Suc n) + setsum (\<lambda>i. f (Suc i)) {0..n}"
lp15@56215
  1072
by (induct n) auto
lp15@56215
  1073
lp15@56215
  1074
lemma complex_taylor:
lp15@61609
  1075
  assumes s: "convex s"
lp15@56215
  1076
      and f: "\<And>i x. x \<in> s \<Longrightarrow> i \<le> n \<Longrightarrow> (f i has_field_derivative f (Suc i) x) (at x within s)"
lp15@56215
  1077
      and B: "\<And>x. x \<in> s \<Longrightarrow> cmod (f (Suc n) x) \<le> B"
lp15@56215
  1078
      and w: "w \<in> s"
lp15@56215
  1079
      and z: "z \<in> s"
lp15@59730
  1080
    shows "cmod(f 0 z - (\<Sum>i\<le>n. f i w * (z-w) ^ i / (fact i)))
lp15@56215
  1081
          \<le> B * cmod(z - w)^(Suc n) / fact n"
lp15@56215
  1082
proof -
lp15@56215
  1083
  have wzs: "closed_segment w z \<subseteq> s" using assms
lp15@56215
  1084
    by (metis convex_contains_segment)
lp15@56215
  1085
  { fix u
lp15@56215
  1086
    assume "u \<in> closed_segment w z"
lp15@56215
  1087
    then have "u \<in> s"
lp15@56215
  1088
      by (metis wzs subsetD)
lp15@59730
  1089
    have "(\<Sum>i\<le>n. f i u * (- of_nat i * (z-u)^(i - 1)) / (fact i) +
lp15@61609
  1090
                      f (Suc i) u * (z-u)^i / (fact i)) =
lp15@59730
  1091
              f (Suc n) u * (z-u) ^ n / (fact n)"
lp15@56215
  1092
    proof (induction n)
lp15@56215
  1093
      case 0 show ?case by simp
lp15@56215
  1094
    next
lp15@56215
  1095
      case (Suc n)
lp15@59730
  1096
      have "(\<Sum>i\<le>Suc n. f i u * (- of_nat i * (z-u) ^ (i - 1)) / (fact i) +
lp15@61609
  1097
                             f (Suc i) u * (z-u) ^ i / (fact i)) =
lp15@59730
  1098
           f (Suc n) u * (z-u) ^ n / (fact n) +
lp15@59730
  1099
           f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n) / (fact (Suc n)) -
lp15@59730
  1100
           f (Suc n) u * ((1 + of_nat n) * (z-u) ^ n) / (fact (Suc n))"
hoelzl@56479
  1101
        using Suc by simp
lp15@59730
  1102
      also have "... = f (Suc (Suc n)) u * (z-u) ^ Suc n / (fact (Suc n))"
lp15@56215
  1103
      proof -
lp15@59730
  1104
        have "(fact(Suc n)) *
lp15@59730
  1105
             (f(Suc n) u *(z-u) ^ n / (fact n) +
lp15@59730
  1106
               f(Suc(Suc n)) u *((z-u) *(z-u) ^ n) / (fact(Suc n)) -
lp15@59730
  1107
               f(Suc n) u *((1 + of_nat n) *(z-u) ^ n) / (fact(Suc n))) =
lp15@59730
  1108
            ((fact(Suc n)) *(f(Suc n) u *(z-u) ^ n)) / (fact n) +
lp15@59730
  1109
            ((fact(Suc n)) *(f(Suc(Suc n)) u *((z-u) *(z-u) ^ n)) / (fact(Suc n))) -
lp15@59730
  1110
            ((fact(Suc n)) *(f(Suc n) u *(of_nat(Suc n) *(z-u) ^ n))) / (fact(Suc n))"
lp15@59730
  1111
          by (simp add: algebra_simps del: fact.simps)
lp15@59730
  1112
        also have "... = ((fact (Suc n)) * (f (Suc n) u * (z-u) ^ n)) / (fact n) +
lp15@59730
  1113
                         (f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n)) -
lp15@59730
  1114
                         (f (Suc n) u * ((1 + of_nat n) * (z-u) ^ n))"
lp15@59730
  1115
          by (simp del: fact.simps)
lp15@59730
  1116
        also have "... = (of_nat (Suc n) * (f (Suc n) u * (z-u) ^ n)) +
lp15@59730
  1117
                         (f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n)) -
lp15@59730
  1118
                         (f (Suc n) u * ((1 + of_nat n) * (z-u) ^ n))"
lp15@59730
  1119
          by (simp only: fact.simps of_nat_mult ac_simps) simp
lp15@56215
  1120
        also have "... = f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n)"
lp15@56215
  1121
          by (simp add: algebra_simps)
lp15@56215
  1122
        finally show ?thesis
lp15@59730
  1123
        by (simp add: mult_left_cancel [where c = "(fact (Suc n))", THEN iffD1] del: fact.simps)
lp15@56215
  1124
      qed
lp15@56215
  1125
      finally show ?case .
lp15@56215
  1126
    qed
lp15@61609
  1127
    then have "((\<lambda>v. (\<Sum>i\<le>n. f i v * (z - v)^i / (fact i)))
lp15@59730
  1128
                has_field_derivative f (Suc n) u * (z-u) ^ n / (fact n))
lp15@56215
  1129
               (at u within s)"
hoelzl@56381
  1130
      apply (intro derivative_eq_intros)
wenzelm@60420
  1131
      apply (blast intro: assms \<open>u \<in> s\<close>)
lp15@56215
  1132
      apply (rule refl)+
lp15@56215
  1133
      apply (auto simp: field_simps)
lp15@56215
  1134
      done
lp15@56215
  1135
  } note sum_deriv = this
lp15@56215
  1136
  { fix u
lp15@56215
  1137
    assume u: "u \<in> closed_segment w z"
lp15@56215
  1138
    then have us: "u \<in> s"
lp15@56215
  1139
      by (metis wzs subsetD)
lp15@56215
  1140
    have "cmod (f (Suc n) u) * cmod (z - u) ^ n \<le> cmod (f (Suc n) u) * cmod (u - z) ^ n"
lp15@56215
  1141
      by (metis norm_minus_commute order_refl)
lp15@56215
  1142
    also have "... \<le> cmod (f (Suc n) u) * cmod (z - w) ^ n"
lp15@56215
  1143
      by (metis mult_left_mono norm_ge_zero power_mono segment_bound [OF u])
lp15@56215
  1144
    also have "... \<le> B * cmod (z - w) ^ n"
lp15@56215
  1145
      by (metis norm_ge_zero zero_le_power mult_right_mono  B [OF us])
lp15@56215
  1146
    finally have "cmod (f (Suc n) u) * cmod (z - u) ^ n \<le> B * cmod (z - w) ^ n" .
lp15@56215
  1147
  } note cmod_bound = this
lp15@59730
  1148
  have "(\<Sum>i\<le>n. f i z * (z - z) ^ i / (fact i)) = (\<Sum>i\<le>n. (f i z / (fact i)) * 0 ^ i)"
lp15@56215
  1149
    by simp
lp15@59730
  1150
  also have "\<dots> = f 0 z / (fact 0)"
lp15@56215
  1151
    by (subst setsum_zero_power) simp
lp15@61609
  1152
  finally have "cmod (f 0 z - (\<Sum>i\<le>n. f i w * (z - w) ^ i / (fact i)))
lp15@59730
  1153
                \<le> cmod ((\<Sum>i\<le>n. f i w * (z - w) ^ i / (fact i)) -
lp15@59730
  1154
                        (\<Sum>i\<le>n. f i z * (z - z) ^ i / (fact i)))"
lp15@56215
  1155
    by (simp add: norm_minus_commute)
lp15@59730
  1156
  also have "... \<le> B * cmod (z - w) ^ n / (fact n) * cmod (w - z)"
lp15@62534
  1157
    apply (rule field_differentiable_bound
lp15@59730
  1158
      [where f' = "\<lambda>w. f (Suc n) w * (z - w)^n / (fact n)"
paulson@61518
  1159
         and s = "closed_segment w z", OF convex_closed_segment])
lp15@61609
  1160
    apply (auto simp: ends_in_segment DERIV_subset [OF sum_deriv wzs]
lp15@56215
  1161
                  norm_divide norm_mult norm_power divide_le_cancel cmod_bound)
lp15@56215
  1162
    done
lp15@59730
  1163
  also have "...  \<le> B * cmod (z - w) ^ Suc n / (fact n)"
lp15@61609
  1164
    by (simp add: algebra_simps norm_minus_commute)
lp15@56215
  1165
  finally show ?thesis .
lp15@56215
  1166
qed
lp15@56215
  1167
lp15@62408
  1168
text\<open>Something more like the traditional MVT for real components\<close>
hoelzl@56370
  1169
lp15@56238
  1170
lemma complex_mvt_line:
hoelzl@56369
  1171
  assumes "\<And>u. u \<in> closed_segment w z \<Longrightarrow> (f has_field_derivative f'(u)) (at u)"
paulson@61518
  1172
    shows "\<exists>u. u \<in> closed_segment w z \<and> Re(f z) - Re(f w) = Re(f'(u) * (z - w))"
lp15@56238
  1173
proof -
lp15@56238
  1174
  have twz: "\<And>t. (1 - t) *\<^sub>R w + t *\<^sub>R z = w + t *\<^sub>R (z - w)"
lp15@56238
  1175
    by (simp add: real_vector.scale_left_diff_distrib real_vector.scale_right_diff_distrib)
hoelzl@56381
  1176
  note assms[unfolded has_field_derivative_def, derivative_intros]
lp15@56238
  1177
  show ?thesis
lp15@56238
  1178
    apply (cut_tac mvt_simple
lp15@56238
  1179
                     [of 0 1 "Re o f o (\<lambda>t. (1 - t) *\<^sub>R w +  t *\<^sub>R z)"
lp15@56238
  1180
                      "\<lambda>u. Re o (\<lambda>h. f'((1 - u) *\<^sub>R w + u *\<^sub>R z) * h) o (\<lambda>t. t *\<^sub>R (z - w))"])
lp15@56238
  1181
    apply auto
lp15@56238
  1182
    apply (rule_tac x="(1 - x) *\<^sub>R w + x *\<^sub>R z" in exI)
paulson@61518
  1183
    apply (auto simp: closed_segment_def twz) []
paulson@61518
  1184
    apply (intro derivative_eq_intros has_derivative_at_within, simp_all)
hoelzl@56369
  1185
    apply (simp add: fun_eq_iff real_vector.scale_right_diff_distrib)
paulson@61518
  1186
    apply (force simp: twz closed_segment_def)
lp15@56238
  1187
    done
lp15@56238
  1188
qed
lp15@56238
  1189
lp15@56238
  1190
lemma complex_taylor_mvt:
lp15@56238
  1191
  assumes "\<And>i x. \<lbrakk>x \<in> closed_segment w z; i \<le> n\<rbrakk> \<Longrightarrow> ((f i) has_field_derivative f (Suc i) x) (at x)"
lp15@56238
  1192
    shows "\<exists>u. u \<in> closed_segment w z \<and>
lp15@56238
  1193
            Re (f 0 z) =
lp15@59730
  1194
            Re ((\<Sum>i = 0..n. f i w * (z - w) ^ i / (fact i)) +
lp15@59730
  1195
                (f (Suc n) u * (z-u)^n / (fact n)) * (z - w))"
lp15@56238
  1196
proof -
lp15@56238
  1197
  { fix u
lp15@56238
  1198
    assume u: "u \<in> closed_segment w z"
lp15@56238
  1199
    have "(\<Sum>i = 0..n.
lp15@56238
  1200
               (f (Suc i) u * (z-u) ^ i - of_nat i * (f i u * (z-u) ^ (i - Suc 0))) /
lp15@59730
  1201
               (fact i)) =
lp15@56238
  1202
          f (Suc 0) u -
lp15@56238
  1203
             (f (Suc (Suc n)) u * ((z-u) ^ Suc n) - (of_nat (Suc n)) * (z-u) ^ n * f (Suc n) u) /
lp15@59730
  1204
             (fact (Suc n)) +
lp15@56238
  1205
             (\<Sum>i = 0..n.
lp15@56238
  1206
                 (f (Suc (Suc i)) u * ((z-u) ^ Suc i) - of_nat (Suc i) * (f (Suc i) u * (z-u) ^ i)) /
lp15@59730
  1207
                 (fact (Suc i)))"
lp15@56238
  1208
       by (subst setsum_Suc_reindex) simp
lp15@56238
  1209
    also have "... = f (Suc 0) u -
lp15@56238
  1210
             (f (Suc (Suc n)) u * ((z-u) ^ Suc n) - (of_nat (Suc n)) * (z-u) ^ n * f (Suc n) u) /
lp15@59730
  1211
             (fact (Suc n)) +
lp15@56238
  1212
             (\<Sum>i = 0..n.
lp15@61609
  1213
                 f (Suc (Suc i)) u * ((z-u) ^ Suc i) / (fact (Suc i))  -
lp15@59730
  1214
                 f (Suc i) u * (z-u) ^ i / (fact i))"
haftmann@57514
  1215
      by (simp only: diff_divide_distrib fact_cancel ac_simps)
lp15@56238
  1216
    also have "... = f (Suc 0) u -
lp15@56238
  1217
             (f (Suc (Suc n)) u * (z-u) ^ Suc n - of_nat (Suc n) * (z-u) ^ n * f (Suc n) u) /
lp15@59730
  1218
             (fact (Suc n)) +
lp15@59730
  1219
             f (Suc (Suc n)) u * (z-u) ^ Suc n / (fact (Suc n)) - f (Suc 0) u"
lp15@56238
  1220
      by (subst setsum_Suc_diff) auto
lp15@59730
  1221
    also have "... = f (Suc n) u * (z-u) ^ n / (fact n)"
lp15@56238
  1222
      by (simp only: algebra_simps diff_divide_distrib fact_cancel)
lp15@61609
  1223
    finally have "(\<Sum>i = 0..n. (f (Suc i) u * (z - u) ^ i
lp15@59730
  1224
                             - of_nat i * (f i u * (z-u) ^ (i - Suc 0))) / (fact i)) =
lp15@59730
  1225
                  f (Suc n) u * (z - u) ^ n / (fact n)" .
lp15@59730
  1226
    then have "((\<lambda>u. \<Sum>i = 0..n. f i u * (z - u) ^ i / (fact i)) has_field_derivative
lp15@59730
  1227
                f (Suc n) u * (z - u) ^ n / (fact n))  (at u)"
hoelzl@56381
  1228
      apply (intro derivative_eq_intros)+
lp15@56238
  1229
      apply (force intro: u assms)
lp15@56238
  1230
      apply (rule refl)+
haftmann@57514
  1231
      apply (auto simp: ac_simps)
lp15@56238
  1232
      done
lp15@56238
  1233
  }
lp15@56238
  1234
  then show ?thesis
lp15@59730
  1235
    apply (cut_tac complex_mvt_line [of w z "\<lambda>u. \<Sum>i = 0..n. f i u * (z-u) ^ i / (fact i)"
lp15@59730
  1236
               "\<lambda>u. (f (Suc n) u * (z-u)^n / (fact n))"])
lp15@56238
  1237
    apply (auto simp add: intro: open_closed_segment)
lp15@56238
  1238
    done
lp15@56238
  1239
qed
lp15@56238
  1240
lp15@60017
  1241
wenzelm@60420
  1242
subsection \<open>Polynomal function extremal theorem, from HOL Light\<close>
lp15@60017
  1243
lp15@60017
  1244
lemma polyfun_extremal_lemma: (*COMPLEX_POLYFUN_EXTREMAL_LEMMA in HOL Light*)
lp15@60017
  1245
    fixes c :: "nat \<Rightarrow> 'a::real_normed_div_algebra"
lp15@60017
  1246
  assumes "0 < e"
lp15@60017
  1247
    shows "\<exists>M. \<forall>z. M \<le> norm(z) \<longrightarrow> norm (\<Sum>i\<le>n. c(i) * z^i) \<le> e * norm(z) ^ (Suc n)"
lp15@60017
  1248
proof (induct n)
lp15@60017
  1249
  case 0 with assms
lp15@60017
  1250
  show ?case
lp15@60017
  1251
    apply (rule_tac x="norm (c 0) / e" in exI)
lp15@60017
  1252
    apply (auto simp: field_simps)
lp15@60017
  1253
    done
lp15@60017
  1254
next
lp15@60017
  1255
  case (Suc n)
lp15@60017
  1256
  obtain M where M: "\<And>z. M \<le> norm z \<Longrightarrow> norm (\<Sum>i\<le>n. c i * z^i) \<le> e * norm z ^ Suc n"
lp15@60017
  1257
    using Suc assms by blast
lp15@60017
  1258
  show ?case
lp15@60017
  1259
  proof (rule exI [where x= "max M (1 + norm(c(Suc n)) / e)"], clarsimp simp del: power_Suc)
lp15@60017
  1260
    fix z::'a
lp15@60017
  1261
    assume z1: "M \<le> norm z" and "1 + norm (c (Suc n)) / e \<le> norm z"
lp15@60017
  1262
    then have z2: "e + norm (c (Suc n)) \<le> e * norm z"
lp15@60017
  1263
      using assms by (simp add: field_simps)
lp15@60017
  1264
    have "norm (\<Sum>i\<le>n. c i * z^i) \<le> e * norm z ^ Suc n"
lp15@60017
  1265
      using M [OF z1] by simp
lp15@60017
  1266
    then have "norm (\<Sum>i\<le>n. c i * z^i) + norm (c (Suc n) * z ^ Suc n) \<le> e * norm z ^ Suc n + norm (c (Suc n) * z ^ Suc n)"
lp15@60017
  1267
      by simp
lp15@60017
  1268
    then have "norm ((\<Sum>i\<le>n. c i * z^i) + c (Suc n) * z ^ Suc n) \<le> e * norm z ^ Suc n + norm (c (Suc n) * z ^ Suc n)"
lp15@60017
  1269
      by (blast intro: norm_triangle_le elim: )
lp15@60017
  1270
    also have "... \<le> (e + norm (c (Suc n))) * norm z ^ Suc n"
lp15@60017
  1271
      by (simp add: norm_power norm_mult algebra_simps)
lp15@60017
  1272
    also have "... \<le> (e * norm z) * norm z ^ Suc n"
lp15@60017
  1273
      by (metis z2 mult.commute mult_left_mono norm_ge_zero norm_power)
lp15@60017
  1274
    finally show "norm ((\<Sum>i\<le>n. c i * z^i) + c (Suc n) * z ^ Suc n) \<le> e * norm z ^ Suc (Suc n)"
lp15@60162
  1275
      by simp
lp15@60017
  1276
  qed
lp15@60017
  1277
qed
lp15@60017
  1278
lp15@60017
  1279
lemma polyfun_extremal: (*COMPLEX_POLYFUN_EXTREMAL in HOL Light*)
lp15@60017
  1280
    fixes c :: "nat \<Rightarrow> 'a::real_normed_div_algebra"
lp15@60017
  1281
  assumes k: "c k \<noteq> 0" "1\<le>k" and kn: "k\<le>n"
lp15@60017
  1282
    shows "eventually (\<lambda>z. norm (\<Sum>i\<le>n. c(i) * z^i) \<ge> B) at_infinity"
lp15@60017
  1283
using kn
lp15@60017
  1284
proof (induction n)
lp15@60017
  1285
  case 0
lp15@60017
  1286
  then show ?case
lp15@60017
  1287
    using k  by simp
lp15@60017
  1288
next
lp15@60017
  1289
  case (Suc m)
lp15@60017
  1290
  let ?even = ?case
lp15@60017
  1291
  show ?even
lp15@60017
  1292
  proof (cases "c (Suc m) = 0")
lp15@60017
  1293
    case True
lp15@60017
  1294
    then show ?even using Suc k
lp15@60017
  1295
      by auto (metis antisym_conv less_eq_Suc_le not_le)
lp15@60017
  1296
  next
lp15@60017
  1297
    case False
lp15@60017
  1298
    then obtain M where M:
lp15@60017
  1299
          "\<And>z. M \<le> norm z \<Longrightarrow> norm (\<Sum>i\<le>m. c i * z^i) \<le> norm (c (Suc m)) / 2 * norm z ^ Suc m"
lp15@60017
  1300
      using polyfun_extremal_lemma [of "norm(c (Suc m)) / 2" c m] Suc
lp15@60017
  1301
      by auto
lp15@60017
  1302
    have "\<exists>b. \<forall>z. b \<le> norm z \<longrightarrow> B \<le> norm (\<Sum>i\<le>Suc m. c i * z^i)"
lp15@60017
  1303
    proof (rule exI [where x="max M (max 1 (\<bar>B\<bar> / (norm(c (Suc m)) / 2)))"], clarsimp simp del: power_Suc)
lp15@60017
  1304
      fix z::'a
lp15@60017
  1305
      assume z1: "M \<le> norm z" "1 \<le> norm z"
lp15@60017
  1306
         and "\<bar>B\<bar> * 2 / norm (c (Suc m)) \<le> norm z"
lp15@60017
  1307
      then have z2: "\<bar>B\<bar> \<le> norm (c (Suc m)) * norm z / 2"
lp15@60017
  1308
        using False by (simp add: field_simps)
lp15@60017
  1309
      have nz: "norm z \<le> norm z ^ Suc m"
wenzelm@60420
  1310
        by (metis \<open>1 \<le> norm z\<close> One_nat_def less_eq_Suc_le power_increasing power_one_right zero_less_Suc)
lp15@60017
  1311
      have *: "\<And>y x. norm (c (Suc m)) * norm z / 2 \<le> norm y - norm x \<Longrightarrow> B \<le> norm (x + y)"
lp15@60017
  1312
        by (metis abs_le_iff add.commute norm_diff_ineq order_trans z2)
lp15@60017
  1313
      have "norm z * norm (c (Suc m)) + 2 * norm (\<Sum>i\<le>m. c i * z^i)
lp15@60017
  1314
            \<le> norm (c (Suc m)) * norm z + norm (c (Suc m)) * norm z ^ Suc m"
lp15@60017
  1315
        using M [of z] Suc z1  by auto
lp15@60017
  1316
      also have "... \<le> 2 * (norm (c (Suc m)) * norm z ^ Suc m)"
lp15@60017
  1317
        using nz by (simp add: mult_mono del: power_Suc)
lp15@60017
  1318
      finally show "B \<le> norm ((\<Sum>i\<le>m. c i * z^i) + c (Suc m) * z ^ Suc m)"
lp15@60017
  1319
        using Suc.IH
lp15@60017
  1320
        apply (auto simp: eventually_at_infinity)
lp15@60017
  1321
        apply (rule *)
lp15@60017
  1322
        apply (simp add: field_simps norm_mult norm_power)
lp15@60017
  1323
        done
lp15@60017
  1324
    qed
lp15@60017
  1325
    then show ?even
lp15@60017
  1326
      by (simp add: eventually_at_infinity)
lp15@60017
  1327
  qed
lp15@60017
  1328
qed
lp15@60017
  1329
lp15@56215
  1330
end