src/HOL/Analysis/Complex_Analysis_Basics.thy
author wenzelm
Mon Mar 25 17:21:26 2019 +0100 (2 months ago)
changeset 69981 3dced198b9ec
parent 69529 4ab9657b3257
child 70136 f03a01a18c6e
permissions -rw-r--r--
more strict AFP properties;
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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 Equivalence_Lebesgue_Henstock_Integration "HOL-Library.Nonpos_Ints"
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begin
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(* TODO FIXME: A lot of the things in here have nothing to do with complex analysis *)
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subsection%unimportant\<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 "(((*) c) has_derivative ((*) c)) F"
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by (rule has_derivative_mult_right [OF has_derivative_ident])
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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_field:
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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 "(*) 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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lemmas has_vector_derivative_real_complex = has_vector_derivative_real_field
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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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  using of_nat_neq_0 by force
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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 vector_derivative_cnj_within:
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  assumes "at x within A \<noteq> bot" and "f differentiable at x within A"
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  shows   "vector_derivative (\<lambda>z. cnj (f z)) (at x within A) = 
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             cnj (vector_derivative f (at x within A))" (is "_ = cnj ?D")
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proof -
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  let ?D = "vector_derivative f (at x within A)"
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  from assms have "(f has_vector_derivative ?D) (at x within A)"
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    by (subst (asm) vector_derivative_works)
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  hence "((\<lambda>x. cnj (f x)) has_vector_derivative cnj ?D) (at x within A)"
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    by (rule has_vector_derivative_cnj)
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  thus ?thesis using assms by (auto dest: vector_derivative_within)
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qed
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lemma vector_derivative_cnj:
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  assumes "f differentiable at x"
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  shows   "vector_derivative (\<lambda>z. cnj (f z)) (at x) = cnj (vector_derivative f (at x))"
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  using assms by (intro vector_derivative_cnj_within) auto
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lemma lambda_zero: "(\<lambda>h::'a::mult_zero. 0) = (*) 0"
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  by auto
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lemma lambda_one: "(\<lambda>x::'a::monoid_mult. x) = (*) 1"
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  by auto
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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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(*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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(* TODO: Move? *)
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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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lemmas DERIV_zero_constant = has_field_derivative_zero_constant
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lemma DERIV_zero_unique:
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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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  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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  "(\<And>x. DERIV f x :> 0) \<Longrightarrow> f x = f a"
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  by (metis DERIV_zero_unique UNIV_I convex_UNIV)
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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 continuous_on_Re
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            continuous_on_Im continuous_on_id continuous_on_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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lemma 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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lemma 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 "\<not> 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 sum_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%important holomorphic_on :: "[complex \<Rightarrow> complex, complex set] \<Rightarrow> bool"
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           (infixl "(holomorphic'_on)" 50)
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  where "f holomorphic_on s \<equiv> \<forall>x\<in>s. f field_differentiable (at x within s)"
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named_theorems%important holomorphic_intros "structural introduction rules for holomorphic_on"
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lemma holomorphic_onI [intro?]: "(\<And>x. x \<in> s \<Longrightarrow> f field_differentiable (at x within s)) \<Longrightarrow> f holomorphic_on s"
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  by (simp add: holomorphic_on_def)
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lemma holomorphic_onD [dest?]: "\<lbrakk>f holomorphic_on s; x \<in> s\<rbrakk> \<Longrightarrow> f field_differentiable (at x within s)"
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  by (simp add: holomorphic_on_def)
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lemma holomorphic_on_imp_differentiable_on:
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    "f holomorphic_on s \<Longrightarrow> f differentiable_on s"
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  unfolding holomorphic_on_def differentiable_on_def
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  by (simp add: field_differentiable_imp_differentiable)
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lemma holomorphic_on_imp_differentiable_at:
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   "\<lbrakk>f holomorphic_on s; open s; x \<in> s\<rbrakk> \<Longrightarrow> f field_differentiable (at x)"
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using at_within_open holomorphic_on_def by fastforce
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lemma holomorphic_on_empty [holomorphic_intros]: "f holomorphic_on {}"
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  by (simp add: holomorphic_on_def)
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lemma holomorphic_on_open:
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    "open s \<Longrightarrow> f holomorphic_on s \<longleftrightarrow> (\<forall>x \<in> s. \<exists>f'. DERIV f x :> f')"
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  by (auto simp: holomorphic_on_def field_differentiable_def has_field_derivative_def at_within_open [of _ s])
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lemma holomorphic_on_imp_continuous_on:
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    "f holomorphic_on s \<Longrightarrow> continuous_on s f"
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  by (metis field_differentiable_imp_continuous_at continuous_on_eq_continuous_within holomorphic_on_def)
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lemma holomorphic_on_subset [elim]:
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    "f holomorphic_on s \<Longrightarrow> t \<subseteq> s \<Longrightarrow> f holomorphic_on t"
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  unfolding holomorphic_on_def
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  by (metis field_differentiable_within_subset subsetD)
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lemma holomorphic_transform: "\<lbrakk>f holomorphic_on s; \<And>x. x \<in> s \<Longrightarrow> f x = g x\<rbrakk> \<Longrightarrow> g holomorphic_on s"
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  by (metis field_differentiable_transform_within linordered_field_no_ub holomorphic_on_def)
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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"
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  by (metis holomorphic_transform)
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lemma holomorphic_on_linear [simp, holomorphic_intros]: "((*) c) holomorphic_on s"
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  unfolding holomorphic_on_def by (metis field_differentiable_linear)
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lp15@62217
   285
lemma holomorphic_on_const [simp, holomorphic_intros]: "(\<lambda>z. c) holomorphic_on s"
lp15@62534
   286
  unfolding holomorphic_on_def by (metis field_differentiable_const)
hoelzl@56370
   287
lp15@62217
   288
lemma holomorphic_on_ident [simp, holomorphic_intros]: "(\<lambda>x. x) holomorphic_on s"
lp15@62534
   289
  unfolding holomorphic_on_def by (metis field_differentiable_ident)
hoelzl@56370
   290
lp15@62217
   291
lemma holomorphic_on_id [simp, holomorphic_intros]: "id holomorphic_on s"
hoelzl@56370
   292
  unfolding id_def by (rule holomorphic_on_ident)
hoelzl@56370
   293
hoelzl@56370
   294
lemma holomorphic_on_compose:
hoelzl@56370
   295
  "f holomorphic_on s \<Longrightarrow> g holomorphic_on (f ` s) \<Longrightarrow> (g o f) holomorphic_on s"
lp15@62534
   296
  using field_differentiable_compose_within[of f _ s g]
hoelzl@56370
   297
  by (auto simp: holomorphic_on_def)
hoelzl@56370
   298
hoelzl@56370
   299
lemma holomorphic_on_compose_gen:
hoelzl@56370
   300
  "f holomorphic_on s \<Longrightarrow> g holomorphic_on t \<Longrightarrow> f ` s \<subseteq> t \<Longrightarrow> (g o f) holomorphic_on s"
hoelzl@56370
   301
  by (metis holomorphic_on_compose holomorphic_on_subset)
hoelzl@56370
   302
eberlm@68721
   303
lemma holomorphic_on_balls_imp_entire:
eberlm@68721
   304
  assumes "\<not>bdd_above A" "\<And>r. r \<in> A \<Longrightarrow> f holomorphic_on ball c r"
eberlm@68721
   305
  shows   "f holomorphic_on B"
eberlm@68721
   306
proof (rule holomorphic_on_subset)
eberlm@68721
   307
  show "f holomorphic_on UNIV" unfolding holomorphic_on_def
eberlm@68721
   308
  proof
eberlm@68721
   309
    fix z :: complex
eberlm@68721
   310
    from \<open>\<not>bdd_above A\<close> obtain r where r: "r \<in> A" "r > norm (z - c)"
eberlm@68721
   311
      by (meson bdd_aboveI not_le)
eberlm@68721
   312
    with assms(2) have "f holomorphic_on ball c r" by blast
eberlm@68721
   313
    moreover from r have "z \<in> ball c r" by (auto simp: dist_norm norm_minus_commute)
eberlm@68721
   314
    ultimately show "f field_differentiable at z"
eberlm@68721
   315
      by (auto simp: holomorphic_on_def at_within_open[of _ "ball c r"])
eberlm@68721
   316
  qed
eberlm@68721
   317
qed auto
eberlm@68721
   318
eberlm@68721
   319
lemma holomorphic_on_balls_imp_entire':
eberlm@68721
   320
  assumes "\<And>r. r > 0 \<Longrightarrow> f holomorphic_on ball c r"
eberlm@68721
   321
  shows   "f holomorphic_on B"
eberlm@68721
   322
proof (rule holomorphic_on_balls_imp_entire)
eberlm@68721
   323
  {
eberlm@68721
   324
    fix M :: real
eberlm@68721
   325
    have "\<exists>x. x > max M 0" by (intro gt_ex)
eberlm@68721
   326
    hence "\<exists>x>0. x > M" by auto
eberlm@68721
   327
  }
eberlm@68721
   328
  thus "\<not>bdd_above {(0::real)<..}" unfolding bdd_above_def
eberlm@68721
   329
    by (auto simp: not_le)
eberlm@68721
   330
qed (insert assms, auto)
eberlm@68721
   331
lp15@61520
   332
lemma holomorphic_on_minus [holomorphic_intros]: "f holomorphic_on s \<Longrightarrow> (\<lambda>z. -(f z)) holomorphic_on s"
lp15@62534
   333
  by (metis field_differentiable_minus holomorphic_on_def)
hoelzl@56370
   334
lp15@61520
   335
lemma holomorphic_on_add [holomorphic_intros]:
hoelzl@56370
   336
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s\<rbrakk> \<Longrightarrow> (\<lambda>z. f z + g z) holomorphic_on s"
lp15@62534
   337
  unfolding holomorphic_on_def by (metis field_differentiable_add)
hoelzl@56370
   338
lp15@61520
   339
lemma holomorphic_on_diff [holomorphic_intros]:
hoelzl@56370
   340
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s\<rbrakk> \<Longrightarrow> (\<lambda>z. f z - g z) holomorphic_on s"
lp15@62534
   341
  unfolding holomorphic_on_def by (metis field_differentiable_diff)
hoelzl@56370
   342
lp15@61520
   343
lemma holomorphic_on_mult [holomorphic_intros]:
hoelzl@56370
   344
  "\<lbrakk>f holomorphic_on s; g holomorphic_on s\<rbrakk> \<Longrightarrow> (\<lambda>z. f z * g z) holomorphic_on s"
lp15@62534
   345
  unfolding holomorphic_on_def by (metis field_differentiable_mult)
hoelzl@56370
   346
lp15@61520
   347
lemma holomorphic_on_inverse [holomorphic_intros]:
hoelzl@56370
   348
  "\<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
   349
  unfolding holomorphic_on_def by (metis field_differentiable_inverse)
hoelzl@56370
   350
lp15@61520
   351
lemma holomorphic_on_divide [holomorphic_intros]:
hoelzl@56370
   352
  "\<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
   353
  unfolding holomorphic_on_def by (metis field_differentiable_divide)
hoelzl@56370
   354
lp15@61520
   355
lemma holomorphic_on_power [holomorphic_intros]:
hoelzl@56370
   356
  "f holomorphic_on s \<Longrightarrow> (\<lambda>z. (f z)^n) holomorphic_on s"
lp15@62534
   357
  unfolding holomorphic_on_def by (metis field_differentiable_power)
hoelzl@56370
   358
nipkow@64267
   359
lemma holomorphic_on_sum [holomorphic_intros]:
nipkow@64267
   360
  "(\<And>i. i \<in> I \<Longrightarrow> (f i) holomorphic_on s) \<Longrightarrow> (\<lambda>x. sum (\<lambda>i. f i x) I) holomorphic_on s"
nipkow@64267
   361
  unfolding holomorphic_on_def by (metis field_differentiable_sum)
hoelzl@56370
   362
eberlm@67135
   363
lemma holomorphic_on_prod [holomorphic_intros]:
eberlm@67135
   364
  "(\<And>i. i \<in> I \<Longrightarrow> (f i) holomorphic_on s) \<Longrightarrow> (\<lambda>x. prod (\<lambda>i. f i x) I) holomorphic_on s"
eberlm@67135
   365
  by (induction I rule: infinite_finite_induct) (auto intro: holomorphic_intros)
eberlm@67135
   366
eberlm@66486
   367
lemma holomorphic_pochhammer [holomorphic_intros]:
eberlm@66486
   368
  "f holomorphic_on A \<Longrightarrow> (\<lambda>s. pochhammer (f s) n) holomorphic_on A"
eberlm@66486
   369
  by (induction n) (auto intro!: holomorphic_intros simp: pochhammer_Suc)
eberlm@66486
   370
eberlm@66486
   371
lemma holomorphic_on_scaleR [holomorphic_intros]:
eberlm@66486
   372
  "f holomorphic_on A \<Longrightarrow> (\<lambda>x. c *\<^sub>R f x) holomorphic_on A"
eberlm@66486
   373
  by (auto simp: scaleR_conv_of_real intro!: holomorphic_intros)
eberlm@66486
   374
eberlm@67167
   375
lemma holomorphic_on_Un [holomorphic_intros]:
eberlm@67167
   376
  assumes "f holomorphic_on A" "f holomorphic_on B" "open A" "open B"
eberlm@67167
   377
  shows   "f holomorphic_on (A \<union> B)"
lp15@68239
   378
  using assms by (auto simp: holomorphic_on_def  at_within_open[of _ A]
eberlm@67167
   379
                             at_within_open[of _ B]  at_within_open[of _ "A \<union> B"] open_Un)
eberlm@67167
   380
eberlm@67167
   381
lemma holomorphic_on_If_Un [holomorphic_intros]:
eberlm@67167
   382
  assumes "f holomorphic_on A" "g holomorphic_on B" "open A" "open B"
eberlm@67167
   383
  assumes "\<And>z. z \<in> A \<Longrightarrow> z \<in> B \<Longrightarrow> f z = g z"
eberlm@67167
   384
  shows   "(\<lambda>z. if z \<in> A then f z else g z) holomorphic_on (A \<union> B)" (is "?h holomorphic_on _")
eberlm@67167
   385
proof (intro holomorphic_on_Un)
eberlm@67167
   386
  note \<open>f holomorphic_on A\<close>
eberlm@67167
   387
  also have "f holomorphic_on A \<longleftrightarrow> ?h holomorphic_on A"
eberlm@67167
   388
    by (intro holomorphic_cong) auto
eberlm@67167
   389
  finally show \<dots> .
eberlm@67167
   390
next
eberlm@67167
   391
  note \<open>g holomorphic_on B\<close>
eberlm@67167
   392
  also have "g holomorphic_on B \<longleftrightarrow> ?h holomorphic_on B"
eberlm@67167
   393
    using assms by (intro holomorphic_cong) auto
eberlm@67167
   394
  finally show \<dots> .
eberlm@67167
   395
qed (insert assms, auto)
eberlm@67167
   396
lp15@67371
   397
lemma leibniz_rule_holomorphic:
lp15@67371
   398
  fixes f::"complex \<Rightarrow> 'b::euclidean_space \<Rightarrow> complex"
lp15@67371
   399
  assumes "\<And>x t. x \<in> U \<Longrightarrow> t \<in> cbox a b \<Longrightarrow> ((\<lambda>x. f x t) has_field_derivative fx x t) (at x within U)"
lp15@67371
   400
  assumes "\<And>x. x \<in> U \<Longrightarrow> (f x) integrable_on cbox a b"
lp15@67371
   401
  assumes "continuous_on (U \<times> (cbox a b)) (\<lambda>(x, t). fx x t)"
lp15@67371
   402
  assumes "convex U"
lp15@67371
   403
  shows "(\<lambda>x. integral (cbox a b) (f x)) holomorphic_on U"
lp15@67371
   404
  using leibniz_rule_field_differentiable[OF assms(1-3) _ assms(4)]
lp15@67371
   405
  by (auto simp: holomorphic_on_def)
lp15@67371
   406
lp15@62534
   407
lemma DERIV_deriv_iff_field_differentiable:
lp15@62534
   408
  "DERIV f x :> deriv f x \<longleftrightarrow> f field_differentiable at x"
lp15@62534
   409
  unfolding field_differentiable_def by (metis DERIV_imp_deriv)
hoelzl@56370
   410
lp15@62533
   411
lemma holomorphic_derivI:
lp15@62533
   412
     "\<lbrakk>f holomorphic_on S; open S; x \<in> S\<rbrakk>
lp15@62533
   413
      \<Longrightarrow> (f has_field_derivative deriv f x) (at x within T)"
lp15@62534
   414
by (metis DERIV_deriv_iff_field_differentiable at_within_open  holomorphic_on_def has_field_derivative_at_within)
lp15@62533
   415
hoelzl@56370
   416
lemma complex_derivative_chain:
lp15@62534
   417
  "f field_differentiable at x \<Longrightarrow> g field_differentiable at (f x)
hoelzl@56370
   418
    \<Longrightarrow> deriv (g o f) x = deriv g (f x) * deriv f x"
lp15@62534
   419
  by (metis DERIV_deriv_iff_field_differentiable DERIV_chain DERIV_imp_deriv)
hoelzl@56370
   420
lp15@62397
   421
lemma deriv_linear [simp]: "deriv (\<lambda>w. c * w) = (\<lambda>z. c)"
hoelzl@56370
   422
  by (metis DERIV_imp_deriv DERIV_cmult_Id)
hoelzl@56370
   423
lp15@62397
   424
lemma deriv_ident [simp]: "deriv (\<lambda>w. w) = (\<lambda>z. 1)"
hoelzl@56370
   425
  by (metis DERIV_imp_deriv DERIV_ident)
hoelzl@56370
   426
lp15@62397
   427
lemma deriv_id [simp]: "deriv id = (\<lambda>z. 1)"
lp15@62397
   428
  by (simp add: id_def)
lp15@62397
   429
lp15@62397
   430
lemma deriv_const [simp]: "deriv (\<lambda>w. c) = (\<lambda>z. 0)"
hoelzl@56370
   431
  by (metis DERIV_imp_deriv DERIV_const)
hoelzl@56370
   432
lp15@62534
   433
lemma deriv_add [simp]:
lp15@62534
   434
  "\<lbrakk>f field_differentiable at z; g field_differentiable at z\<rbrakk>
hoelzl@56370
   435
   \<Longrightarrow> deriv (\<lambda>w. f w + g w) z = deriv f z + deriv g z"
lp15@62534
   436
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   437
  by (auto intro!: DERIV_imp_deriv derivative_intros)
hoelzl@56370
   438
lp15@62534
   439
lemma deriv_diff [simp]:
lp15@62534
   440
  "\<lbrakk>f field_differentiable at z; g field_differentiable at z\<rbrakk>
hoelzl@56370
   441
   \<Longrightarrow> deriv (\<lambda>w. f w - g w) z = deriv f z - deriv g z"
lp15@62534
   442
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   443
  by (auto intro!: DERIV_imp_deriv derivative_intros)
hoelzl@56370
   444
lp15@62534
   445
lemma deriv_mult [simp]:
lp15@62534
   446
  "\<lbrakk>f field_differentiable at z; g field_differentiable at z\<rbrakk>
hoelzl@56370
   447
   \<Longrightarrow> deriv (\<lambda>w. f w * g w) z = f z * deriv g z + deriv f z * g z"
lp15@62534
   448
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
hoelzl@56381
   449
  by (auto intro!: DERIV_imp_deriv derivative_eq_intros)
hoelzl@56370
   450
lp15@68255
   451
lemma deriv_cmult:
lp15@62534
   452
  "f field_differentiable at z \<Longrightarrow> deriv (\<lambda>w. c * f w) z = c * deriv f z"
lp15@68255
   453
  by simp
hoelzl@56370
   454
lp15@68255
   455
lemma deriv_cmult_right:
lp15@62534
   456
  "f field_differentiable at z \<Longrightarrow> deriv (\<lambda>w. f w * c) z = deriv f z * c"
lp15@68255
   457
  by simp
lp15@68255
   458
lp15@68255
   459
lemma deriv_inverse [simp]:
lp15@68255
   460
  "\<lbrakk>f field_differentiable at z; f z \<noteq> 0\<rbrakk>
lp15@68255
   461
   \<Longrightarrow> deriv (\<lambda>w. inverse (f w)) z = - deriv f z / f z ^ 2"
lp15@62534
   462
  unfolding DERIV_deriv_iff_field_differentiable[symmetric]
lp15@68255
   463
  by (safe intro!: DERIV_imp_deriv derivative_eq_intros) (auto simp: divide_simps power2_eq_square)
hoelzl@56370
   464
lp15@68255
   465
lemma deriv_divide [simp]:
lp15@68255
   466
  "\<lbrakk>f field_differentiable at z; g field_differentiable at z; g z \<noteq> 0\<rbrakk>
lp15@68255
   467
   \<Longrightarrow> deriv (\<lambda>w. f w / g w) z = (deriv f z * g z - f z * deriv g z) / g z ^ 2"
lp15@68255
   468
  by (simp add: field_class.field_divide_inverse field_differentiable_inverse)
lp15@68255
   469
     (simp add: divide_simps power2_eq_square)
lp15@68255
   470
lp15@68255
   471
lemma deriv_cdivide_right:
lp15@62534
   472
  "f field_differentiable at z \<Longrightarrow> deriv (\<lambda>w. f w / c) z = deriv f z / c"
lp15@68255
   473
  by (simp add: field_class.field_divide_inverse)
lp15@62217
   474
hoelzl@56370
   475
lemma complex_derivative_transform_within_open:
lp15@61609
   476
  "\<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
   477
   \<Longrightarrow> deriv f z = deriv g z"
hoelzl@56370
   478
  unfolding holomorphic_on_def
hoelzl@56370
   479
  by (rule DERIV_imp_deriv)
lp15@62534
   480
     (metis DERIV_deriv_iff_field_differentiable DERIV_transform_within_open at_within_open)
hoelzl@56370
   481
lp15@62534
   482
lemma deriv_compose_linear:
lp15@62534
   483
  "f field_differentiable at (c * z) \<Longrightarrow> deriv (\<lambda>w. f (c * w)) z = c * deriv f (c * z)"
hoelzl@56370
   484
apply (rule DERIV_imp_deriv)
lp15@68255
   485
  unfolding DERIV_deriv_iff_field_differentiable [symmetric]
lp15@68255
   486
  by (metis (full_types) DERIV_chain2 DERIV_cmult_Id mult.commute)
lp15@68255
   487
hoelzl@56370
   488
lp15@62533
   489
lemma nonzero_deriv_nonconstant:
lp15@62533
   490
  assumes df: "DERIV f \<xi> :> df" and S: "open S" "\<xi> \<in> S" and "df \<noteq> 0"
lp15@62533
   491
    shows "\<not> f constant_on S"
lp15@62533
   492
unfolding constant_on_def
lp15@62533
   493
by (metis \<open>df \<noteq> 0\<close> DERIV_transform_within_open [OF df S] DERIV_const DERIV_unique)
lp15@62533
   494
lp15@62533
   495
lemma holomorphic_nonconstant:
lp15@62533
   496
  assumes holf: "f holomorphic_on S" and "open S" "\<xi> \<in> S" "deriv f \<xi> \<noteq> 0"
lp15@62533
   497
    shows "\<not> f constant_on S"
lp15@68255
   498
  by (rule nonzero_deriv_nonconstant [of f "deriv f \<xi>" \<xi> S])
lp15@68255
   499
    (use assms in \<open>auto simp: holomorphic_derivI\<close>)
lp15@62533
   500
eberlm@69180
   501
subsection%unimportant\<open>Caratheodory characterization\<close>
lp15@64394
   502
lp15@64394
   503
lemma field_differentiable_caratheodory_at:
lp15@64394
   504
  "f field_differentiable (at z) \<longleftrightarrow>
lp15@64394
   505
         (\<exists>g. (\<forall>w. f(w) - f(z) = g(w) * (w - z)) \<and> continuous (at z) g)"
lp15@64394
   506
  using CARAT_DERIV [of f]
lp15@64394
   507
  by (simp add: field_differentiable_def has_field_derivative_def)
lp15@64394
   508
lp15@64394
   509
lemma field_differentiable_caratheodory_within:
lp15@64394
   510
  "f field_differentiable (at z within s) \<longleftrightarrow>
lp15@64394
   511
         (\<exists>g. (\<forall>w. f(w) - f(z) = g(w) * (w - z)) \<and> continuous (at z within s) g)"
lp15@64394
   512
  using DERIV_caratheodory_within [of f]
lp15@64394
   513
  by (simp add: field_differentiable_def has_field_derivative_def)
lp15@64394
   514
wenzelm@60420
   515
subsection\<open>Analyticity on a set\<close>
lp15@56215
   516
eberlm@69180
   517
definition%important analytic_on (infixl "(analytic'_on)" 50)
lp15@68255
   518
  where "f analytic_on S \<equiv> \<forall>x \<in> S. \<exists>e. 0 < e \<and> f holomorphic_on (ball x e)"
lp15@56215
   519
eberlm@69180
   520
named_theorems%important analytic_intros "introduction rules for proving analyticity"
lp15@65587
   521
lp15@68255
   522
lemma analytic_imp_holomorphic: "f analytic_on S \<Longrightarrow> f holomorphic_on S"
hoelzl@56370
   523
  by (simp add: at_within_open [OF _ open_ball] analytic_on_def holomorphic_on_def)
lp15@62534
   524
     (metis centre_in_ball field_differentiable_at_within)
lp15@56215
   525
lp15@68255
   526
lemma analytic_on_open: "open S \<Longrightarrow> f analytic_on S \<longleftrightarrow> f holomorphic_on S"
lp15@56215
   527
apply (auto simp: analytic_imp_holomorphic)
lp15@56215
   528
apply (auto simp: analytic_on_def holomorphic_on_def)
lp15@56215
   529
by (metis holomorphic_on_def holomorphic_on_subset open_contains_ball)
lp15@56215
   530
lp15@56215
   531
lemma analytic_on_imp_differentiable_at:
lp15@68255
   532
  "f analytic_on S \<Longrightarrow> x \<in> S \<Longrightarrow> f field_differentiable (at x)"
hoelzl@56370
   533
 apply (auto simp: analytic_on_def holomorphic_on_def)
lp15@66827
   534
by (metis open_ball centre_in_ball field_differentiable_within_open)
lp15@56215
   535
lp15@68255
   536
lemma analytic_on_subset: "f analytic_on S \<Longrightarrow> T \<subseteq> S \<Longrightarrow> f analytic_on T"
lp15@56215
   537
  by (auto simp: analytic_on_def)
lp15@56215
   538
lp15@68255
   539
lemma analytic_on_Un: "f analytic_on (S \<union> T) \<longleftrightarrow> f analytic_on S \<and> f analytic_on T"
lp15@56215
   540
  by (auto simp: analytic_on_def)
lp15@56215
   541
lp15@68255
   542
lemma analytic_on_Union: "f analytic_on (\<Union>\<T>) \<longleftrightarrow> (\<forall>T \<in> \<T>. f analytic_on T)"
hoelzl@56370
   543
  by (auto simp: analytic_on_def)
hoelzl@56370
   544
lp15@68255
   545
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
   546
  by (auto simp: analytic_on_def)
lp15@61609
   547
lp15@56215
   548
lemma analytic_on_holomorphic:
lp15@68255
   549
  "f analytic_on S \<longleftrightarrow> (\<exists>T. open T \<and> S \<subseteq> T \<and> f holomorphic_on T)"
lp15@56215
   550
  (is "?lhs = ?rhs")
lp15@56215
   551
proof -
lp15@68255
   552
  have "?lhs \<longleftrightarrow> (\<exists>T. open T \<and> S \<subseteq> T \<and> f analytic_on T)"
lp15@56215
   553
  proof safe
lp15@68255
   554
    assume "f analytic_on S"
lp15@68255
   555
    then show "\<exists>T. open T \<and> S \<subseteq> T \<and> f analytic_on T"
lp15@56215
   556
      apply (simp add: analytic_on_def)
lp15@68255
   557
      apply (rule exI [where x="\<Union>{U. open U \<and> f analytic_on U}"], auto)
lp15@66827
   558
      apply (metis open_ball analytic_on_open centre_in_ball)
lp15@56215
   559
      by (metis analytic_on_def)
lp15@56215
   560
  next
lp15@68255
   561
    fix T
lp15@68255
   562
    assume "open T" "S \<subseteq> T" "f analytic_on T"
lp15@68255
   563
    then show "f analytic_on S"
lp15@56215
   564
        by (metis analytic_on_subset)
lp15@56215
   565
  qed
lp15@56215
   566
  also have "... \<longleftrightarrow> ?rhs"
lp15@56215
   567
    by (auto simp: analytic_on_open)
lp15@56215
   568
  finally show ?thesis .
lp15@56215
   569
qed
lp15@56215
   570
nipkow@69064
   571
lemma analytic_on_linear [analytic_intros,simp]: "((*) c) analytic_on S"
lp15@65587
   572
  by (auto simp add: analytic_on_holomorphic)
lp15@56215
   573
lp15@68255
   574
lemma analytic_on_const [analytic_intros,simp]: "(\<lambda>z. c) analytic_on S"
hoelzl@56370
   575
  by (metis analytic_on_def holomorphic_on_const zero_less_one)
hoelzl@56370
   576
lp15@68255
   577
lemma analytic_on_ident [analytic_intros,simp]: "(\<lambda>x. x) analytic_on S"
lp15@65587
   578
  by (simp add: analytic_on_def gt_ex)
lp15@56215
   579
lp15@68255
   580
lemma analytic_on_id [analytic_intros]: "id analytic_on S"
hoelzl@56370
   581
  unfolding id_def by (rule analytic_on_ident)
lp15@56215
   582
lp15@56215
   583
lemma analytic_on_compose:
lp15@68255
   584
  assumes f: "f analytic_on S"
lp15@68255
   585
      and g: "g analytic_on (f ` S)"
lp15@68255
   586
    shows "(g o f) analytic_on S"
lp15@56215
   587
unfolding analytic_on_def
lp15@56215
   588
proof (intro ballI)
lp15@56215
   589
  fix x
lp15@68255
   590
  assume x: "x \<in> S"
lp15@56215
   591
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball x e" using f
lp15@56215
   592
    by (metis analytic_on_def)
lp15@56215
   593
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball (f x) e'" using g
lp15@61609
   594
    by (metis analytic_on_def g image_eqI x)
lp15@56215
   595
  have "isCont f x"
lp15@62534
   596
    by (metis analytic_on_imp_differentiable_at field_differentiable_imp_continuous_at f x)
lp15@56215
   597
  with e' obtain d where d: "0 < d" and fd: "f ` ball x d \<subseteq> ball (f x) e'"
lp15@56215
   598
     by (auto simp: continuous_at_ball)
lp15@61609
   599
  have "g \<circ> f holomorphic_on ball x (min d e)"
lp15@56215
   600
    apply (rule holomorphic_on_compose)
lp15@56215
   601
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   602
    by (metis fd gh holomorphic_on_subset image_mono min.cobounded1 subset_ball)
lp15@56215
   603
  then show "\<exists>e>0. g \<circ> f holomorphic_on ball x e"
lp15@61609
   604
    by (metis d e min_less_iff_conj)
lp15@56215
   605
qed
lp15@56215
   606
lp15@56215
   607
lemma analytic_on_compose_gen:
lp15@68255
   608
  "f analytic_on S \<Longrightarrow> g analytic_on T \<Longrightarrow> (\<And>z. z \<in> S \<Longrightarrow> f z \<in> T)
lp15@68255
   609
             \<Longrightarrow> g o f analytic_on S"
lp15@56215
   610
by (metis analytic_on_compose analytic_on_subset image_subset_iff)
lp15@56215
   611
lp15@65587
   612
lemma analytic_on_neg [analytic_intros]:
lp15@68255
   613
  "f analytic_on S \<Longrightarrow> (\<lambda>z. -(f z)) analytic_on S"
lp15@56215
   614
by (metis analytic_on_holomorphic holomorphic_on_minus)
lp15@56215
   615
lp15@65587
   616
lemma analytic_on_add [analytic_intros]:
lp15@68255
   617
  assumes f: "f analytic_on S"
lp15@68255
   618
      and g: "g analytic_on S"
lp15@68255
   619
    shows "(\<lambda>z. f z + g z) analytic_on S"
lp15@56215
   620
unfolding analytic_on_def
lp15@56215
   621
proof (intro ballI)
lp15@56215
   622
  fix z
lp15@68255
   623
  assume z: "z \<in> S"
lp15@56215
   624
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   625
    by (metis analytic_on_def)
lp15@56215
   626
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball z e'" using g
lp15@61609
   627
    by (metis analytic_on_def g z)
lp15@61609
   628
  have "(\<lambda>z. f z + g z) holomorphic_on ball z (min e e')"
lp15@61609
   629
    apply (rule holomorphic_on_add)
lp15@56215
   630
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   631
    by (metis gh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   632
  then show "\<exists>e>0. (\<lambda>z. f z + g z) holomorphic_on ball z e"
lp15@56215
   633
    by (metis e e' min_less_iff_conj)
lp15@56215
   634
qed
lp15@56215
   635
lp15@65587
   636
lemma analytic_on_diff [analytic_intros]:
lp15@68255
   637
  assumes f: "f analytic_on S"
lp15@68255
   638
      and g: "g analytic_on S"
lp15@68255
   639
    shows "(\<lambda>z. f z - g z) analytic_on S"
lp15@56215
   640
unfolding analytic_on_def
lp15@56215
   641
proof (intro ballI)
lp15@56215
   642
  fix z
lp15@68255
   643
  assume z: "z \<in> S"
lp15@56215
   644
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   645
    by (metis analytic_on_def)
lp15@56215
   646
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball z e'" using g
lp15@61609
   647
    by (metis analytic_on_def g z)
lp15@61609
   648
  have "(\<lambda>z. f z - g z) holomorphic_on ball z (min e e')"
lp15@61609
   649
    apply (rule holomorphic_on_diff)
lp15@56215
   650
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   651
    by (metis gh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   652
  then show "\<exists>e>0. (\<lambda>z. f z - g z) holomorphic_on ball z e"
lp15@56215
   653
    by (metis e e' min_less_iff_conj)
lp15@56215
   654
qed
lp15@56215
   655
lp15@65587
   656
lemma analytic_on_mult [analytic_intros]:
lp15@68255
   657
  assumes f: "f analytic_on S"
lp15@68255
   658
      and g: "g analytic_on S"
lp15@68255
   659
    shows "(\<lambda>z. f z * g z) analytic_on S"
lp15@56215
   660
unfolding analytic_on_def
lp15@56215
   661
proof (intro ballI)
lp15@56215
   662
  fix z
lp15@68255
   663
  assume z: "z \<in> S"
lp15@56215
   664
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   665
    by (metis analytic_on_def)
lp15@56215
   666
  obtain e' where e': "0 < e'" and gh: "g holomorphic_on ball z e'" using g
lp15@61609
   667
    by (metis analytic_on_def g z)
lp15@61609
   668
  have "(\<lambda>z. f z * g z) holomorphic_on ball z (min e e')"
lp15@61609
   669
    apply (rule holomorphic_on_mult)
lp15@56215
   670
    apply (metis fh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   671
    by (metis gh holomorphic_on_subset min.bounded_iff order_refl subset_ball)
lp15@56215
   672
  then show "\<exists>e>0. (\<lambda>z. f z * g z) holomorphic_on ball z e"
lp15@56215
   673
    by (metis e e' min_less_iff_conj)
lp15@56215
   674
qed
lp15@56215
   675
lp15@65587
   676
lemma analytic_on_inverse [analytic_intros]:
lp15@68255
   677
  assumes f: "f analytic_on S"
lp15@68255
   678
      and nz: "(\<And>z. z \<in> S \<Longrightarrow> f z \<noteq> 0)"
lp15@68255
   679
    shows "(\<lambda>z. inverse (f z)) analytic_on S"
lp15@56215
   680
unfolding analytic_on_def
lp15@56215
   681
proof (intro ballI)
lp15@56215
   682
  fix z
lp15@68255
   683
  assume z: "z \<in> S"
lp15@56215
   684
  then obtain e where e: "0 < e" and fh: "f holomorphic_on ball z e" using f
lp15@56215
   685
    by (metis analytic_on_def)
lp15@56215
   686
  have "continuous_on (ball z e) f"
lp15@56215
   687
    by (metis fh holomorphic_on_imp_continuous_on)
lp15@61609
   688
  then obtain e' where e': "0 < e'" and nz': "\<And>y. dist z y < e' \<Longrightarrow> f y \<noteq> 0"
lp15@66827
   689
    by (metis open_ball centre_in_ball continuous_on_open_avoid e z nz)
lp15@61609
   690
  have "(\<lambda>z. inverse (f z)) holomorphic_on ball z (min e e')"
lp15@56215
   691
    apply (rule holomorphic_on_inverse)
lp15@56215
   692
    apply (metis fh holomorphic_on_subset min.cobounded2 min.commute subset_ball)
lp15@61609
   693
    by (metis nz' mem_ball min_less_iff_conj)
lp15@56215
   694
  then show "\<exists>e>0. (\<lambda>z. inverse (f z)) holomorphic_on ball z e"
lp15@56215
   695
    by (metis e e' min_less_iff_conj)
lp15@56215
   696
qed
lp15@56215
   697
lp15@65587
   698
lemma analytic_on_divide [analytic_intros]:
lp15@68255
   699
  assumes f: "f analytic_on S"
lp15@68255
   700
      and g: "g analytic_on S"
lp15@68255
   701
      and nz: "(\<And>z. z \<in> S \<Longrightarrow> g z \<noteq> 0)"
lp15@68255
   702
    shows "(\<lambda>z. f z / g z) analytic_on S"
lp15@56215
   703
unfolding divide_inverse
lp15@56215
   704
by (metis analytic_on_inverse analytic_on_mult f g nz)
lp15@56215
   705
lp15@65587
   706
lemma analytic_on_power [analytic_intros]:
lp15@68255
   707
  "f analytic_on S \<Longrightarrow> (\<lambda>z. (f z) ^ n) analytic_on S"
lp15@65587
   708
by (induct n) (auto simp: analytic_on_mult)
lp15@56215
   709
lp15@65587
   710
lemma analytic_on_sum [analytic_intros]:
lp15@68255
   711
  "(\<And>i. i \<in> I \<Longrightarrow> (f i) analytic_on S) \<Longrightarrow> (\<lambda>x. sum (\<lambda>i. f i x) I) analytic_on S"
hoelzl@56369
   712
  by (induct I rule: infinite_finite_induct) (auto simp: analytic_on_const analytic_on_add)
lp15@56215
   713
lp15@62408
   714
lemma deriv_left_inverse:
lp15@62408
   715
  assumes "f holomorphic_on S" and "g holomorphic_on T"
lp15@62408
   716
      and "open S" and "open T"
lp15@62408
   717
      and "f ` S \<subseteq> T"
lp15@62408
   718
      and [simp]: "\<And>z. z \<in> S \<Longrightarrow> g (f z) = z"
lp15@62408
   719
      and "w \<in> S"
lp15@62408
   720
    shows "deriv f w * deriv g (f w) = 1"
lp15@62408
   721
proof -
lp15@62408
   722
  have "deriv f w * deriv g (f w) = deriv g (f w) * deriv f w"
lp15@62408
   723
    by (simp add: algebra_simps)
lp15@62408
   724
  also have "... = deriv (g o f) w"
lp15@62408
   725
    using assms
lp15@62408
   726
    by (metis analytic_on_imp_differentiable_at analytic_on_open complex_derivative_chain image_subset_iff)
lp15@62408
   727
  also have "... = deriv id w"
lp15@68255
   728
  proof (rule complex_derivative_transform_within_open [where s=S])
lp15@68255
   729
    show "g \<circ> f holomorphic_on S"
lp15@68255
   730
      by (rule assms holomorphic_on_compose_gen holomorphic_intros)+
lp15@68255
   731
  qed (use assms in auto)
lp15@62408
   732
  also have "... = 1"
lp15@62408
   733
    by simp
lp15@62408
   734
  finally show ?thesis .
lp15@62408
   735
qed
lp15@62408
   736
eberlm@69180
   737
subsection%unimportant\<open>Analyticity at a point\<close>
lp15@56215
   738
lp15@56215
   739
lemma analytic_at_ball:
lp15@56215
   740
  "f analytic_on {z} \<longleftrightarrow> (\<exists>e. 0<e \<and> f holomorphic_on ball z e)"
lp15@56215
   741
by (metis analytic_on_def singleton_iff)
lp15@56215
   742
lp15@56215
   743
lemma analytic_at:
lp15@56215
   744
    "f analytic_on {z} \<longleftrightarrow> (\<exists>s. open s \<and> z \<in> s \<and> f holomorphic_on s)"
lp15@56215
   745
by (metis analytic_on_holomorphic empty_subsetI insert_subset)
lp15@56215
   746
lp15@56215
   747
lemma analytic_on_analytic_at:
lp15@56215
   748
    "f analytic_on s \<longleftrightarrow> (\<forall>z \<in> s. f analytic_on {z})"
lp15@56215
   749
by (metis analytic_at_ball analytic_on_def)
lp15@56215
   750
lp15@56215
   751
lemma analytic_at_two:
lp15@56215
   752
  "f analytic_on {z} \<and> g analytic_on {z} \<longleftrightarrow>
lp15@56215
   753
   (\<exists>s. open s \<and> z \<in> s \<and> f holomorphic_on s \<and> g holomorphic_on s)"
lp15@56215
   754
  (is "?lhs = ?rhs")
lp15@61609
   755
proof
lp15@56215
   756
  assume ?lhs
lp15@61609
   757
  then obtain s t
lp15@56215
   758
    where st: "open s" "z \<in> s" "f holomorphic_on s"
lp15@56215
   759
              "open t" "z \<in> t" "g holomorphic_on t"
lp15@56215
   760
    by (auto simp: analytic_at)
lp15@56215
   761
  show ?rhs
lp15@56215
   762
    apply (rule_tac x="s \<inter> t" in exI)
lp15@56215
   763
    using st
nipkow@69286
   764
    apply (auto simp: holomorphic_on_subset)
lp15@56215
   765
    done
lp15@56215
   766
next
lp15@61609
   767
  assume ?rhs
lp15@56215
   768
  then show ?lhs
lp15@56215
   769
    by (force simp add: analytic_at)
lp15@56215
   770
qed
lp15@56215
   771
eberlm@69180
   772
subsection%unimportant\<open>Combining theorems for derivative with ``analytic at'' hypotheses\<close>
lp15@56215
   773
lp15@61609
   774
lemma
lp15@56215
   775
  assumes "f analytic_on {z}" "g analytic_on {z}"
hoelzl@56370
   776
  shows complex_derivative_add_at: "deriv (\<lambda>w. f w + g w) z = deriv f z + deriv g z"
hoelzl@56370
   777
    and complex_derivative_diff_at: "deriv (\<lambda>w. f w - g w) z = deriv f z - deriv g z"
hoelzl@56370
   778
    and complex_derivative_mult_at: "deriv (\<lambda>w. f w * g w) z =
hoelzl@56370
   779
           f z * deriv g z + deriv f z * g z"
lp15@56215
   780
proof -
lp15@56215
   781
  obtain s where s: "open s" "z \<in> s" "f holomorphic_on s" "g holomorphic_on s"
lp15@56215
   782
    using assms by (metis analytic_at_two)
hoelzl@56370
   783
  show "deriv (\<lambda>w. f w + g w) z = deriv f z + deriv g z"
hoelzl@56370
   784
    apply (rule DERIV_imp_deriv [OF DERIV_add])
lp15@56215
   785
    using s
lp15@62534
   786
    apply (auto simp: holomorphic_on_open field_differentiable_def DERIV_deriv_iff_field_differentiable)
lp15@56215
   787
    done
hoelzl@56370
   788
  show "deriv (\<lambda>w. f w - g w) z = deriv f z - deriv g z"
hoelzl@56370
   789
    apply (rule DERIV_imp_deriv [OF DERIV_diff])
lp15@56215
   790
    using s
lp15@62534
   791
    apply (auto simp: holomorphic_on_open field_differentiable_def DERIV_deriv_iff_field_differentiable)
lp15@56215
   792
    done
hoelzl@56370
   793
  show "deriv (\<lambda>w. f w * g w) z = f z * deriv g z + deriv f z * g z"
hoelzl@56370
   794
    apply (rule DERIV_imp_deriv [OF DERIV_mult'])
lp15@56215
   795
    using s
lp15@62534
   796
    apply (auto simp: holomorphic_on_open field_differentiable_def DERIV_deriv_iff_field_differentiable)
lp15@56215
   797
    done
lp15@56215
   798
qed
lp15@56215
   799
lp15@62534
   800
lemma deriv_cmult_at:
hoelzl@56370
   801
  "f analytic_on {z} \<Longrightarrow>  deriv (\<lambda>w. c * f w) z = c * deriv f z"
lp15@61848
   802
by (auto simp: complex_derivative_mult_at deriv_const analytic_on_const)
lp15@56215
   803
lp15@62534
   804
lemma deriv_cmult_right_at:
hoelzl@56370
   805
  "f analytic_on {z} \<Longrightarrow>  deriv (\<lambda>w. f w * c) z = deriv f z * c"
lp15@61848
   806
by (auto simp: complex_derivative_mult_at deriv_const analytic_on_const)
lp15@56215
   807
eberlm@69180
   808
subsection%unimportant\<open>Complex differentiation of sequences and series\<close>
lp15@56215
   809
eberlm@61531
   810
(* TODO: Could probably be simplified using Uniform_Limit *)
lp15@56215
   811
lemma has_complex_derivative_sequence:
lp15@68255
   812
  fixes S :: "complex set"
lp15@68255
   813
  assumes cvs: "convex S"
lp15@68255
   814
      and df:  "\<And>n x. x \<in> S \<Longrightarrow> (f n has_field_derivative f' n x) (at x within S)"
lp15@68255
   815
      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"
lp15@68255
   816
      and "\<exists>x l. x \<in> S \<and> ((\<lambda>n. f n x) \<longlongrightarrow> l) sequentially"
lp15@68255
   817
    shows "\<exists>g. \<forall>x \<in> S. ((\<lambda>n. f n x) \<longlongrightarrow> g x) sequentially \<and>
lp15@68255
   818
                       (g has_field_derivative (g' x)) (at x within S)"
lp15@56215
   819
proof -
lp15@68255
   820
  from assms obtain x l where x: "x \<in> S" and tf: "((\<lambda>n. f n x) \<longlongrightarrow> l) sequentially"
lp15@56215
   821
    by blast
lp15@56215
   822
  { fix e::real assume e: "e > 0"
lp15@68255
   823
    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
   824
      by (metis conv)
lp15@68255
   825
    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
   826
    proof (rule exI [of _ N], clarify)
lp15@56215
   827
      fix n y h
lp15@68255
   828
      assume "N \<le> n" "y \<in> S"
lp15@56215
   829
      then have "cmod (f' n y - g' y) \<le> e"
lp15@56215
   830
        by (metis N)
lp15@56215
   831
      then have "cmod h * cmod (f' n y - g' y) \<le> cmod h * e"
lp15@56215
   832
        by (auto simp: antisym_conv2 mult_le_cancel_left norm_triangle_ineq2)
lp15@56215
   833
      then show "cmod (f' n y * h - g' y * h) \<le> e * cmod h"
lp15@56215
   834
        by (simp add: norm_mult [symmetric] field_simps)
lp15@56215
   835
    qed
lp15@56215
   836
  } note ** = this
lp15@56215
   837
  show ?thesis
lp15@68055
   838
    unfolding has_field_derivative_def
lp15@56215
   839
  proof (rule has_derivative_sequence [OF cvs _ _ x])
lp15@68239
   840
    show "(\<lambda>n. f n x) \<longlonglongrightarrow> l"
lp15@68239
   841
      by (rule tf)
lp15@68255
   842
  next show "\<And>e. e > 0 \<Longrightarrow> \<forall>\<^sub>F n in sequentially. \<forall>x\<in>S. \<forall>h. cmod (f' n x * h - g' x * h) \<le> e * cmod h"
lp15@68239
   843
      unfolding eventually_sequentially by (blast intro: **)
lp15@68055
   844
  qed (metis has_field_derivative_def df)
lp15@56215
   845
qed
lp15@56215
   846
lp15@56215
   847
lemma has_complex_derivative_series:
lp15@68255
   848
  fixes S :: "complex set"
lp15@68255
   849
  assumes cvs: "convex S"
lp15@68255
   850
      and df:  "\<And>n x. x \<in> S \<Longrightarrow> (f n has_field_derivative f' n x) (at x within S)"
lp15@68255
   851
      and conv: "\<And>e. 0 < e \<Longrightarrow> \<exists>N. \<forall>n x. n \<ge> N \<longrightarrow> x \<in> S
lp15@56215
   852
                \<longrightarrow> cmod ((\<Sum>i<n. f' i x) - g' x) \<le> e"
lp15@68255
   853
      and "\<exists>x l. x \<in> S \<and> ((\<lambda>n. f n x) sums l)"
lp15@68255
   854
    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
   855
proof -
lp15@68255
   856
  from assms obtain x l where x: "x \<in> S" and sf: "((\<lambda>n. f n x) sums l)"
lp15@56215
   857
    by blast
lp15@56215
   858
  { fix e::real assume e: "e > 0"
lp15@68255
   859
    then obtain N where N: "\<forall>n x. n \<ge> N \<longrightarrow> x \<in> S
lp15@56215
   860
            \<longrightarrow> cmod ((\<Sum>i<n. f' i x) - g' x) \<le> e"
lp15@61609
   861
      by (metis conv)
lp15@68255
   862
    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
   863
    proof (rule exI [of _ N], clarify)
lp15@56215
   864
      fix n y h
lp15@68255
   865
      assume "N \<le> n" "y \<in> S"
lp15@56215
   866
      then have "cmod ((\<Sum>i<n. f' i y) - g' y) \<le> e"
lp15@56215
   867
        by (metis N)
lp15@56215
   868
      then have "cmod h * cmod ((\<Sum>i<n. f' i y) - g' y) \<le> cmod h * e"
lp15@56215
   869
        by (auto simp: antisym_conv2 mult_le_cancel_left norm_triangle_ineq2)
lp15@56215
   870
      then show "cmod ((\<Sum>i<n. h * f' i y) - g' y * h) \<le> e * cmod h"
nipkow@64267
   871
        by (simp add: norm_mult [symmetric] field_simps sum_distrib_left)
lp15@56215
   872
    qed
lp15@56215
   873
  } note ** = this
lp15@56215
   874
  show ?thesis
lp15@56215
   875
  unfolding has_field_derivative_def
lp15@56215
   876
  proof (rule has_derivative_series [OF cvs _ _ x])
lp15@56215
   877
    fix n x
lp15@68255
   878
    assume "x \<in> S"
lp15@68255
   879
    then show "((f n) has_derivative (\<lambda>z. z * f' n x)) (at x within S)"
lp15@56215
   880
      by (metis df has_field_derivative_def mult_commute_abs)
lp15@56215
   881
  next show " ((\<lambda>n. f n x) sums l)"
lp15@56215
   882
    by (rule sf)
lp15@68255
   883
  next show "\<And>e. e>0 \<Longrightarrow> \<forall>\<^sub>F n in sequentially. \<forall>x\<in>S. \<forall>h. cmod ((\<Sum>i<n. h * f' i x) - g' x * h) \<le> e * cmod h"
lp15@68239
   884
      unfolding eventually_sequentially by (blast intro: **)
lp15@56215
   885
  qed
lp15@56215
   886
qed
lp15@56215
   887
eberlm@61531
   888
lp15@62534
   889
lemma field_differentiable_series:
immler@66252
   890
  fixes f :: "nat \<Rightarrow> 'a::{real_normed_field,banach} \<Rightarrow> 'a"
lp15@68255
   891
  assumes "convex S" "open S"
lp15@68255
   892
  assumes "\<And>n x. x \<in> S \<Longrightarrow> (f n has_field_derivative f' n x) (at x)"
lp15@68255
   893
  assumes "uniformly_convergent_on S (\<lambda>n x. \<Sum>i<n. f' i x)"
lp15@68255
   894
  assumes "x0 \<in> S" "summable (\<lambda>n. f n x0)" and x: "x \<in> S"
lp15@68055
   895
  shows  "(\<lambda>x. \<Sum>n. f n x) field_differentiable (at x)"
eberlm@61531
   896
proof -
lp15@68255
   897
  from assms(4) obtain g' where A: "uniform_limit S (\<lambda>n x. \<Sum>i<n. f' i x) g' sequentially"
eberlm@61531
   898
    unfolding uniformly_convergent_on_def by blast
lp15@68255
   899
  from x and \<open>open S\<close> have S: "at x within S = at x" by (rule at_within_open)
lp15@68255
   900
  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)"
lp15@68255
   901
    by (intro has_field_derivative_series[of S f f' g' x0] assms A has_field_derivative_at_within)
lp15@68255
   902
  then obtain g where g: "\<And>x. x \<in> S \<Longrightarrow> (\<lambda>n. f n x) sums g x"
lp15@68255
   903
    "\<And>x. x \<in> S \<Longrightarrow> (g has_field_derivative g' x) (at x within S)" by blast
nipkow@69064
   904
  from g(2)[OF x] have g': "(g has_derivative (*) (g' x)) (at x)"
lp15@68255
   905
    by (simp add: has_field_derivative_def S)
nipkow@69064
   906
  have "((\<lambda>x. \<Sum>n. f n x) has_derivative (*) (g' x)) (at x)"
lp15@68255
   907
    by (rule has_derivative_transform_within_open[OF g' \<open>open S\<close> x])
eberlm@61531
   908
       (insert g, auto simp: sums_iff)
lp15@62534
   909
  thus "(\<lambda>x. \<Sum>n. f n x) field_differentiable (at x)" unfolding differentiable_def
lp15@62534
   910
    by (auto simp: summable_def field_differentiable_def has_field_derivative_def)
eberlm@61531
   911
qed
eberlm@61531
   912
eberlm@69180
   913
subsection%unimportant\<open>Bound theorem\<close>
lp15@56215
   914
lp15@62534
   915
lemma field_differentiable_bound:
lp15@68255
   916
  fixes S :: "'a::real_normed_field set"
lp15@68255
   917
  assumes cvs: "convex S"
lp15@68255
   918
      and df:  "\<And>z. z \<in> S \<Longrightarrow> (f has_field_derivative f' z) (at z within S)"
lp15@68255
   919
      and dn:  "\<And>z. z \<in> S \<Longrightarrow> norm (f' z) \<le> B"
lp15@68255
   920
      and "x \<in> S"  "y \<in> S"
lp15@56215
   921
    shows "norm(f x - f y) \<le> B * norm(x - y)"
lp15@56215
   922
  apply (rule differentiable_bound [OF cvs])
lp15@68239
   923
  apply (erule df [unfolded has_field_derivative_def])
lp15@68239
   924
  apply (rule onorm_le, simp_all add: norm_mult mult_right_mono assms)
lp15@56215
   925
  done
lp15@56215
   926
eberlm@69180
   927
subsection%unimportant\<open>Inverse function theorem for complex derivatives\<close>
lp15@56215
   928
immler@66252
   929
lemma has_field_derivative_inverse_basic:
lp15@56215
   930
  shows "DERIV f (g y) :> f' \<Longrightarrow>
lp15@56215
   931
        f' \<noteq> 0 \<Longrightarrow>
lp15@56215
   932
        continuous (at y) g \<Longrightarrow>
lp15@56215
   933
        open t \<Longrightarrow>
lp15@56215
   934
        y \<in> t \<Longrightarrow>
lp15@56215
   935
        (\<And>z. z \<in> t \<Longrightarrow> f (g z) = z)
lp15@56215
   936
        \<Longrightarrow> DERIV g y :> inverse (f')"
lp15@56215
   937
  unfolding has_field_derivative_def
lp15@56215
   938
  apply (rule has_derivative_inverse_basic)
lp15@56215
   939
  apply (auto simp:  bounded_linear_mult_right)
lp15@56215
   940
  done
lp15@56215
   941
immler@66252
   942
lemma has_field_derivative_inverse_strong:
immler@66252
   943
  fixes f :: "'a::{euclidean_space,real_normed_field} \<Rightarrow> 'a"
lp15@56215
   944
  shows "DERIV f x :> f' \<Longrightarrow>
lp15@56215
   945
         f' \<noteq> 0 \<Longrightarrow>
lp15@68255
   946
         open S \<Longrightarrow>
lp15@68255
   947
         x \<in> S \<Longrightarrow>
lp15@68255
   948
         continuous_on S f \<Longrightarrow>
lp15@68255
   949
         (\<And>z. z \<in> S \<Longrightarrow> g (f z) = z)
lp15@56215
   950
         \<Longrightarrow> DERIV g (f x) :> inverse (f')"
lp15@56215
   951
  unfolding has_field_derivative_def
lp15@68255
   952
  apply (rule has_derivative_inverse_strong [of S x f g ])
lp15@56215
   953
  by auto
lp15@56215
   954
immler@66252
   955
lemma has_field_derivative_inverse_strong_x:
immler@66252
   956
  fixes f :: "'a::{euclidean_space,real_normed_field} \<Rightarrow> 'a"
lp15@56215
   957
  shows  "DERIV f (g y) :> f' \<Longrightarrow>
lp15@56215
   958
          f' \<noteq> 0 \<Longrightarrow>
lp15@68255
   959
          open S \<Longrightarrow>
lp15@68255
   960
          continuous_on S f \<Longrightarrow>
lp15@68255
   961
          g y \<in> S \<Longrightarrow> f(g y) = y \<Longrightarrow>
lp15@68255
   962
          (\<And>z. z \<in> S \<Longrightarrow> g (f z) = z)
lp15@56215
   963
          \<Longrightarrow> DERIV g y :> inverse (f')"
lp15@56215
   964
  unfolding has_field_derivative_def
lp15@68255
   965
  apply (rule has_derivative_inverse_strong_x [of S g y f])
lp15@56215
   966
  by auto
lp15@56215
   967
eberlm@69180
   968
subsection%unimportant \<open>Taylor on Complex Numbers\<close>
lp15@56215
   969
nipkow@64267
   970
lemma sum_Suc_reindex:
lp15@56215
   971
  fixes f :: "nat \<Rightarrow> 'a::ab_group_add"
nipkow@64267
   972
    shows  "sum f {0..n} = f 0 - f (Suc n) + sum (\<lambda>i. f (Suc i)) {0..n}"
lp15@56215
   973
by (induct n) auto
lp15@56215
   974
nipkow@69529
   975
lemma field_Taylor:
lp15@68255
   976
  assumes S: "convex S"
lp15@68255
   977
      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@68255
   978
      and B: "\<And>x. x \<in> S \<Longrightarrow> norm (f (Suc n) x) \<le> B"
lp15@68255
   979
      and w: "w \<in> S"
lp15@68255
   980
      and z: "z \<in> S"
immler@66252
   981
    shows "norm(f 0 z - (\<Sum>i\<le>n. f i w * (z-w) ^ i / (fact i)))
immler@66252
   982
          \<le> B * norm(z - w)^(Suc n) / fact n"
lp15@56215
   983
proof -
lp15@68255
   984
  have wzs: "closed_segment w z \<subseteq> S" using assms
lp15@56215
   985
    by (metis convex_contains_segment)
lp15@56215
   986
  { fix u
lp15@56215
   987
    assume "u \<in> closed_segment w z"
lp15@68255
   988
    then have "u \<in> S"
lp15@56215
   989
      by (metis wzs subsetD)
lp15@59730
   990
    have "(\<Sum>i\<le>n. f i u * (- of_nat i * (z-u)^(i - 1)) / (fact i) +
lp15@61609
   991
                      f (Suc i) u * (z-u)^i / (fact i)) =
lp15@59730
   992
              f (Suc n) u * (z-u) ^ n / (fact n)"
lp15@56215
   993
    proof (induction n)
lp15@56215
   994
      case 0 show ?case by simp
lp15@56215
   995
    next
lp15@56215
   996
      case (Suc n)
lp15@59730
   997
      have "(\<Sum>i\<le>Suc n. f i u * (- of_nat i * (z-u) ^ (i - 1)) / (fact i) +
lp15@61609
   998
                             f (Suc i) u * (z-u) ^ i / (fact i)) =
lp15@59730
   999
           f (Suc n) u * (z-u) ^ n / (fact n) +
lp15@59730
  1000
           f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n) / (fact (Suc n)) -
lp15@59730
  1001
           f (Suc n) u * ((1 + of_nat n) * (z-u) ^ n) / (fact (Suc n))"
hoelzl@56479
  1002
        using Suc by simp
lp15@59730
  1003
      also have "... = f (Suc (Suc n)) u * (z-u) ^ Suc n / (fact (Suc n))"
lp15@56215
  1004
      proof -
lp15@59730
  1005
        have "(fact(Suc n)) *
lp15@59730
  1006
             (f(Suc n) u *(z-u) ^ n / (fact n) +
lp15@59730
  1007
               f(Suc(Suc n)) u *((z-u) *(z-u) ^ n) / (fact(Suc n)) -
lp15@59730
  1008
               f(Suc n) u *((1 + of_nat n) *(z-u) ^ n) / (fact(Suc n))) =
lp15@59730
  1009
            ((fact(Suc n)) *(f(Suc n) u *(z-u) ^ n)) / (fact n) +
lp15@59730
  1010
            ((fact(Suc n)) *(f(Suc(Suc n)) u *((z-u) *(z-u) ^ n)) / (fact(Suc n))) -
lp15@59730
  1011
            ((fact(Suc n)) *(f(Suc n) u *(of_nat(Suc n) *(z-u) ^ n))) / (fact(Suc n))"
haftmann@63367
  1012
          by (simp add: algebra_simps del: fact_Suc)
lp15@59730
  1013
        also have "... = ((fact (Suc n)) * (f (Suc n) u * (z-u) ^ n)) / (fact n) +
lp15@59730
  1014
                         (f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n)) -
lp15@59730
  1015
                         (f (Suc n) u * ((1 + of_nat n) * (z-u) ^ n))"
haftmann@63367
  1016
          by (simp del: fact_Suc)
lp15@59730
  1017
        also have "... = (of_nat (Suc n) * (f (Suc n) u * (z-u) ^ n)) +
lp15@59730
  1018
                         (f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n)) -
lp15@59730
  1019
                         (f (Suc n) u * ((1 + of_nat n) * (z-u) ^ n))"
haftmann@63367
  1020
          by (simp only: fact_Suc of_nat_mult ac_simps) simp
lp15@56215
  1021
        also have "... = f (Suc (Suc n)) u * ((z-u) * (z-u) ^ n)"
lp15@56215
  1022
          by (simp add: algebra_simps)
lp15@56215
  1023
        finally show ?thesis
haftmann@63367
  1024
        by (simp add: mult_left_cancel [where c = "(fact (Suc n))", THEN iffD1] del: fact_Suc)
lp15@56215
  1025
      qed
lp15@56215
  1026
      finally show ?case .
lp15@56215
  1027
    qed
lp15@61609
  1028
    then have "((\<lambda>v. (\<Sum>i\<le>n. f i v * (z - v)^i / (fact i)))
lp15@59730
  1029
                has_field_derivative f (Suc n) u * (z-u) ^ n / (fact n))
lp15@68255
  1030
               (at u within S)"
hoelzl@56381
  1031
      apply (intro derivative_eq_intros)
lp15@68255
  1032
      apply (blast intro: assms \<open>u \<in> S\<close>)
lp15@56215
  1033
      apply (rule refl)+
lp15@56215
  1034
      apply (auto simp: field_simps)
lp15@56215
  1035
      done
lp15@56215
  1036
  } note sum_deriv = this
lp15@56215
  1037
  { fix u
lp15@56215
  1038
    assume u: "u \<in> closed_segment w z"
lp15@68255
  1039
    then have us: "u \<in> S"
lp15@56215
  1040
      by (metis wzs subsetD)
immler@66252
  1041
    have "norm (f (Suc n) u) * norm (z - u) ^ n \<le> norm (f (Suc n) u) * norm (u - z) ^ n"
lp15@56215
  1042
      by (metis norm_minus_commute order_refl)
immler@66252
  1043
    also have "... \<le> norm (f (Suc n) u) * norm (z - w) ^ n"
lp15@56215
  1044
      by (metis mult_left_mono norm_ge_zero power_mono segment_bound [OF u])
immler@66252
  1045
    also have "... \<le> B * norm (z - w) ^ n"
lp15@56215
  1046
      by (metis norm_ge_zero zero_le_power mult_right_mono  B [OF us])
immler@66252
  1047
    finally have "norm (f (Suc n) u) * norm (z - u) ^ n \<le> B * norm (z - w) ^ n" .
lp15@56215
  1048
  } note cmod_bound = this
lp15@59730
  1049
  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
  1050
    by simp
lp15@59730
  1051
  also have "\<dots> = f 0 z / (fact 0)"
nipkow@64267
  1052
    by (subst sum_zero_power) simp
immler@66252
  1053
  finally have "norm (f 0 z - (\<Sum>i\<le>n. f i w * (z - w) ^ i / (fact i)))
immler@66252
  1054
                \<le> norm ((\<Sum>i\<le>n. f i w * (z - w) ^ i / (fact i)) -
lp15@59730
  1055
                        (\<Sum>i\<le>n. f i z * (z - z) ^ i / (fact i)))"
lp15@56215
  1056
    by (simp add: norm_minus_commute)
immler@66252
  1057
  also have "... \<le> B * norm (z - w) ^ n / (fact n) * norm (w - z)"
lp15@62534
  1058
    apply (rule field_differentiable_bound
lp15@59730
  1059
      [where f' = "\<lambda>w. f (Suc n) w * (z - w)^n / (fact n)"
lp15@68255
  1060
         and S = "closed_segment w z", OF convex_closed_segment])
lp15@61609
  1061
    apply (auto simp: ends_in_segment DERIV_subset [OF sum_deriv wzs]
lp15@56215
  1062
                  norm_divide norm_mult norm_power divide_le_cancel cmod_bound)
lp15@56215
  1063
    done
immler@66252
  1064
  also have "...  \<le> B * norm (z - w) ^ Suc n / (fact n)"
lp15@61609
  1065
    by (simp add: algebra_simps norm_minus_commute)
lp15@56215
  1066
  finally show ?thesis .
lp15@56215
  1067
qed
lp15@56215
  1068
nipkow@69529
  1069
lemma complex_Taylor:
lp15@68255
  1070
  assumes S: "convex S"
lp15@68255
  1071
      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@68255
  1072
      and B: "\<And>x. x \<in> S \<Longrightarrow> cmod (f (Suc n) x) \<le> B"
lp15@68255
  1073
      and w: "w \<in> S"
lp15@68255
  1074
      and z: "z \<in> S"
immler@66252
  1075
    shows "cmod(f 0 z - (\<Sum>i\<le>n. f i w * (z-w) ^ i / (fact i)))
immler@66252
  1076
          \<le> B * cmod(z - w)^(Suc n) / fact n"
nipkow@69529
  1077
  using assms by (rule field_Taylor)
immler@66252
  1078
immler@66252
  1079
lp15@62408
  1080
text\<open>Something more like the traditional MVT for real components\<close>
hoelzl@56370
  1081
lp15@56238
  1082
lemma complex_mvt_line:
hoelzl@56369
  1083
  assumes "\<And>u. u \<in> closed_segment w z \<Longrightarrow> (f has_field_derivative f'(u)) (at u)"
paulson@61518
  1084
    shows "\<exists>u. u \<in> closed_segment w z \<and> Re(f z) - Re(f w) = Re(f'(u) * (z - w))"
lp15@56238
  1085
proof -
lp15@56238
  1086
  have twz: "\<And>t. (1 - t) *\<^sub>R w + t *\<^sub>R z = w + t *\<^sub>R (z - w)"
lp15@56238
  1087
    by (simp add: real_vector.scale_left_diff_distrib real_vector.scale_right_diff_distrib)
hoelzl@56381
  1088
  note assms[unfolded has_field_derivative_def, derivative_intros]
lp15@56238
  1089
  show ?thesis
lp15@56238
  1090
    apply (cut_tac mvt_simple
lp15@56238
  1091
                     [of 0 1 "Re o f o (\<lambda>t. (1 - t) *\<^sub>R w +  t *\<^sub>R z)"
lp15@56238
  1092
                      "\<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
  1093
    apply auto
lp15@56238
  1094
    apply (rule_tac x="(1 - x) *\<^sub>R w + x *\<^sub>R z" in exI)
paulson@61518
  1095
    apply (auto simp: closed_segment_def twz) []
lp15@67979
  1096
    apply (intro derivative_eq_intros has_derivative_at_withinI, simp_all)
hoelzl@56369
  1097
    apply (simp add: fun_eq_iff real_vector.scale_right_diff_distrib)
paulson@61518
  1098
    apply (force simp: twz closed_segment_def)
lp15@56238
  1099
    done
lp15@56238
  1100
qed
lp15@56238
  1101
nipkow@69529
  1102
lemma complex_Taylor_mvt:
lp15@56238
  1103
  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
  1104
    shows "\<exists>u. u \<in> closed_segment w z \<and>
lp15@56238
  1105
            Re (f 0 z) =
lp15@59730
  1106
            Re ((\<Sum>i = 0..n. f i w * (z - w) ^ i / (fact i)) +
lp15@59730
  1107
                (f (Suc n) u * (z-u)^n / (fact n)) * (z - w))"
lp15@56238
  1108
proof -
lp15@56238
  1109
  { fix u
lp15@56238
  1110
    assume u: "u \<in> closed_segment w z"
lp15@56238
  1111
    have "(\<Sum>i = 0..n.
lp15@56238
  1112
               (f (Suc i) u * (z-u) ^ i - of_nat i * (f i u * (z-u) ^ (i - Suc 0))) /
lp15@59730
  1113
               (fact i)) =
lp15@56238
  1114
          f (Suc 0) u -
lp15@56238
  1115
             (f (Suc (Suc n)) u * ((z-u) ^ Suc n) - (of_nat (Suc n)) * (z-u) ^ n * f (Suc n) u) /
lp15@59730
  1116
             (fact (Suc n)) +
lp15@56238
  1117
             (\<Sum>i = 0..n.
lp15@56238
  1118
                 (f (Suc (Suc i)) u * ((z-u) ^ Suc i) - of_nat (Suc i) * (f (Suc i) u * (z-u) ^ i)) /
lp15@59730
  1119
                 (fact (Suc i)))"
nipkow@64267
  1120
       by (subst sum_Suc_reindex) simp
lp15@56238
  1121
    also have "... = f (Suc 0) u -
lp15@56238
  1122
             (f (Suc (Suc n)) u * ((z-u) ^ Suc n) - (of_nat (Suc n)) * (z-u) ^ n * f (Suc n) u) /
lp15@59730
  1123
             (fact (Suc n)) +
lp15@56238
  1124
             (\<Sum>i = 0..n.
lp15@61609
  1125
                 f (Suc (Suc i)) u * ((z-u) ^ Suc i) / (fact (Suc i))  -
lp15@59730
  1126
                 f (Suc i) u * (z-u) ^ i / (fact i))"
haftmann@57514
  1127
      by (simp only: diff_divide_distrib fact_cancel ac_simps)
lp15@56238
  1128
    also have "... = f (Suc 0) u -
lp15@56238
  1129
             (f (Suc (Suc n)) u * (z-u) ^ Suc n - of_nat (Suc n) * (z-u) ^ n * f (Suc n) u) /
lp15@59730
  1130
             (fact (Suc n)) +
lp15@59730
  1131
             f (Suc (Suc n)) u * (z-u) ^ Suc n / (fact (Suc n)) - f (Suc 0) u"
nipkow@64267
  1132
      by (subst sum_Suc_diff) auto
lp15@59730
  1133
    also have "... = f (Suc n) u * (z-u) ^ n / (fact n)"
lp15@56238
  1134
      by (simp only: algebra_simps diff_divide_distrib fact_cancel)
lp15@61609
  1135
    finally have "(\<Sum>i = 0..n. (f (Suc i) u * (z - u) ^ i
lp15@59730
  1136
                             - of_nat i * (f i u * (z-u) ^ (i - Suc 0))) / (fact i)) =
lp15@59730
  1137
                  f (Suc n) u * (z - u) ^ n / (fact n)" .
lp15@59730
  1138
    then have "((\<lambda>u. \<Sum>i = 0..n. f i u * (z - u) ^ i / (fact i)) has_field_derivative
lp15@59730
  1139
                f (Suc n) u * (z - u) ^ n / (fact n))  (at u)"
hoelzl@56381
  1140
      apply (intro derivative_eq_intros)+
lp15@56238
  1141
      apply (force intro: u assms)
lp15@56238
  1142
      apply (rule refl)+
haftmann@57514
  1143
      apply (auto simp: ac_simps)
lp15@56238
  1144
      done
lp15@56238
  1145
  }
lp15@56238
  1146
  then show ?thesis
lp15@59730
  1147
    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
  1148
               "\<lambda>u. (f (Suc n) u * (z-u)^n / (fact n))"])
lp15@56238
  1149
    apply (auto simp add: intro: open_closed_segment)
lp15@56238
  1150
    done
lp15@56238
  1151
qed
lp15@56238
  1152
lp15@60017
  1153
eberlm@69180
  1154
subsection%unimportant \<open>Polynomal function extremal theorem, from HOL Light\<close>
lp15@60017
  1155
lp15@60017
  1156
lemma polyfun_extremal_lemma: (*COMPLEX_POLYFUN_EXTREMAL_LEMMA in HOL Light*)
lp15@60017
  1157
    fixes c :: "nat \<Rightarrow> 'a::real_normed_div_algebra"
lp15@60017
  1158
  assumes "0 < e"
lp15@60017
  1159
    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
  1160
proof (induct n)
lp15@60017
  1161
  case 0 with assms
lp15@60017
  1162
  show ?case
lp15@60017
  1163
    apply (rule_tac x="norm (c 0) / e" in exI)
lp15@60017
  1164
    apply (auto simp: field_simps)
lp15@60017
  1165
    done
lp15@60017
  1166
next
lp15@60017
  1167
  case (Suc n)
lp15@60017
  1168
  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
  1169
    using Suc assms by blast
lp15@60017
  1170
  show ?case
lp15@60017
  1171
  proof (rule exI [where x= "max M (1 + norm(c(Suc n)) / e)"], clarsimp simp del: power_Suc)
lp15@60017
  1172
    fix z::'a
lp15@60017
  1173
    assume z1: "M \<le> norm z" and "1 + norm (c (Suc n)) / e \<le> norm z"
lp15@60017
  1174
    then have z2: "e + norm (c (Suc n)) \<le> e * norm z"
lp15@60017
  1175
      using assms by (simp add: field_simps)
lp15@60017
  1176
    have "norm (\<Sum>i\<le>n. c i * z^i) \<le> e * norm z ^ Suc n"
lp15@60017
  1177
      using M [OF z1] by simp
lp15@60017
  1178
    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
  1179
      by simp
lp15@60017
  1180
    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
  1181
      by (blast intro: norm_triangle_le elim: )
lp15@60017
  1182
    also have "... \<le> (e + norm (c (Suc n))) * norm z ^ Suc n"
lp15@60017
  1183
      by (simp add: norm_power norm_mult algebra_simps)
lp15@60017
  1184
    also have "... \<le> (e * norm z) * norm z ^ Suc n"
lp15@60017
  1185
      by (metis z2 mult.commute mult_left_mono norm_ge_zero norm_power)
lp15@60017
  1186
    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
  1187
      by simp
lp15@60017
  1188
  qed
lp15@60017
  1189
qed
lp15@60017
  1190
lp15@60017
  1191
lemma polyfun_extremal: (*COMPLEX_POLYFUN_EXTREMAL in HOL Light*)
lp15@60017
  1192
    fixes c :: "nat \<Rightarrow> 'a::real_normed_div_algebra"
lp15@60017
  1193
  assumes k: "c k \<noteq> 0" "1\<le>k" and kn: "k\<le>n"
lp15@60017
  1194
    shows "eventually (\<lambda>z. norm (\<Sum>i\<le>n. c(i) * z^i) \<ge> B) at_infinity"
lp15@60017
  1195
using kn
lp15@60017
  1196
proof (induction n)
lp15@60017
  1197
  case 0
lp15@60017
  1198
  then show ?case
lp15@60017
  1199
    using k  by simp
lp15@60017
  1200
next
lp15@60017
  1201
  case (Suc m)
lp15@60017
  1202
  let ?even = ?case
lp15@60017
  1203
  show ?even
lp15@60017
  1204
  proof (cases "c (Suc m) = 0")
lp15@60017
  1205
    case True
lp15@60017
  1206
    then show ?even using Suc k
lp15@60017
  1207
      by auto (metis antisym_conv less_eq_Suc_le not_le)
lp15@60017
  1208
  next
lp15@60017
  1209
    case False
lp15@60017
  1210
    then obtain M where M:
lp15@60017
  1211
          "\<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
  1212
      using polyfun_extremal_lemma [of "norm(c (Suc m)) / 2" c m] Suc
lp15@60017
  1213
      by auto
lp15@60017
  1214
    have "\<exists>b. \<forall>z. b \<le> norm z \<longrightarrow> B \<le> norm (\<Sum>i\<le>Suc m. c i * z^i)"
lp15@60017
  1215
    proof (rule exI [where x="max M (max 1 (\<bar>B\<bar> / (norm(c (Suc m)) / 2)))"], clarsimp simp del: power_Suc)
lp15@60017
  1216
      fix z::'a
lp15@60017
  1217
      assume z1: "M \<le> norm z" "1 \<le> norm z"
lp15@60017
  1218
         and "\<bar>B\<bar> * 2 / norm (c (Suc m)) \<le> norm z"
lp15@60017
  1219
      then have z2: "\<bar>B\<bar> \<le> norm (c (Suc m)) * norm z / 2"
lp15@60017
  1220
        using False by (simp add: field_simps)
lp15@60017
  1221
      have nz: "norm z \<le> norm z ^ Suc m"
wenzelm@60420
  1222
        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
  1223
      have *: "\<And>y x. norm (c (Suc m)) * norm z / 2 \<le> norm y - norm x \<Longrightarrow> B \<le> norm (x + y)"
lp15@60017
  1224
        by (metis abs_le_iff add.commute norm_diff_ineq order_trans z2)
lp15@60017
  1225
      have "norm z * norm (c (Suc m)) + 2 * norm (\<Sum>i\<le>m. c i * z^i)
lp15@60017
  1226
            \<le> norm (c (Suc m)) * norm z + norm (c (Suc m)) * norm z ^ Suc m"
lp15@60017
  1227
        using M [of z] Suc z1  by auto
lp15@60017
  1228
      also have "... \<le> 2 * (norm (c (Suc m)) * norm z ^ Suc m)"
lp15@60017
  1229
        using nz by (simp add: mult_mono del: power_Suc)
lp15@60017
  1230
      finally show "B \<le> norm ((\<Sum>i\<le>m. c i * z^i) + c (Suc m) * z ^ Suc m)"
lp15@60017
  1231
        using Suc.IH
lp15@60017
  1232
        apply (auto simp: eventually_at_infinity)
lp15@60017
  1233
        apply (rule *)
lp15@60017
  1234
        apply (simp add: field_simps norm_mult norm_power)
lp15@60017
  1235
        done
lp15@60017
  1236
    qed
lp15@60017
  1237
    then show ?even
lp15@60017
  1238
      by (simp add: eventually_at_infinity)
lp15@60017
  1239
  qed
lp15@60017
  1240
qed
lp15@60017
  1241
lp15@56215
  1242
end