src/HOL/Complex.thy
author paulson <lp15@cam.ac.uk>
Tue Apr 25 17:10:17 2017 +0100 (2017-04-25)
changeset 65579 52eafedaf196
parent 65578 e4997c181cce
child 65583 8d53b3bebab4
permissions -rw-r--r--
Fixed LaTeX issue
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(*  Title:       HOL/Complex.thy
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    Author:      Jacques D. Fleuriot, 2001 University of Edinburgh
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    Author:      Lawrence C Paulson, 2003/4
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*)
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section \<open>Complex Numbers: Rectangular and Polar Representations\<close>
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theory Complex
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imports Transcendental
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begin
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text \<open>
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  We use the \<^theory_text>\<open>codatatype\<close> command to define the type of complex numbers. This
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  allows us to use \<^theory_text>\<open>primcorec\<close> to define complex functions by defining their
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  real and imaginary result separately.
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\<close>
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codatatype complex = Complex (Re: real) (Im: real)
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lemma complex_surj: "Complex (Re z) (Im z) = z"
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  by (rule complex.collapse)
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lemma complex_eqI [intro?]: "Re x = Re y \<Longrightarrow> Im x = Im y \<Longrightarrow> x = y"
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  by (rule complex.expand) simp
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lemma complex_eq_iff: "x = y \<longleftrightarrow> Re x = Re y \<and> Im x = Im y"
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  by (auto intro: complex.expand)
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subsection \<open>Addition and Subtraction\<close>
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instantiation complex :: ab_group_add
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begin
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primcorec zero_complex
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  where
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    "Re 0 = 0"
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  | "Im 0 = 0"
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primcorec plus_complex
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  where
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    "Re (x + y) = Re x + Re y"
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  | "Im (x + y) = Im x + Im y"
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primcorec uminus_complex
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  where
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    "Re (- x) = - Re x"
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  | "Im (- x) = - Im x"
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primcorec minus_complex
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  where
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    "Re (x - y) = Re x - Re y"
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  | "Im (x - y) = Im x - Im y"
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instance
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  by standard (simp_all add: complex_eq_iff)
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end
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subsection \<open>Multiplication and Division\<close>
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instantiation complex :: field
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begin
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primcorec one_complex
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  where
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    "Re 1 = 1"
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  | "Im 1 = 0"
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primcorec times_complex
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  where
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    "Re (x * y) = Re x * Re y - Im x * Im y"
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  | "Im (x * y) = Re x * Im y + Im x * Re y"
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primcorec inverse_complex
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  where
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    "Re (inverse x) = Re x / ((Re x)\<^sup>2 + (Im x)\<^sup>2)"
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  | "Im (inverse x) = - Im x / ((Re x)\<^sup>2 + (Im x)\<^sup>2)"
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definition "x div y = x * inverse y" for x y :: complex
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instance
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  by standard
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     (simp_all add: complex_eq_iff divide_complex_def
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      distrib_left distrib_right right_diff_distrib left_diff_distrib
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      power2_eq_square add_divide_distrib [symmetric])
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end
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lemma Re_divide: "Re (x / y) = (Re x * Re y + Im x * Im y) / ((Re y)\<^sup>2 + (Im y)\<^sup>2)"
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  by (simp add: divide_complex_def add_divide_distrib)
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lemma Im_divide: "Im (x / y) = (Im x * Re y - Re x * Im y) / ((Re y)\<^sup>2 + (Im y)\<^sup>2)"
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  unfolding divide_complex_def times_complex.sel inverse_complex.sel
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  by (simp add: divide_simps)
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lemma Re_power2: "Re (x ^ 2) = (Re x)^2 - (Im x)^2"
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  by (simp add: power2_eq_square)
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lemma Im_power2: "Im (x ^ 2) = 2 * Re x * Im x"
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  by (simp add: power2_eq_square)
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lemma Re_power_real [simp]: "Im x = 0 \<Longrightarrow> Re (x ^ n) = Re x ^ n "
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  by (induct n) simp_all
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lemma Im_power_real [simp]: "Im x = 0 \<Longrightarrow> Im (x ^ n) = 0"
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  by (induct n) simp_all
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subsection \<open>Scalar Multiplication\<close>
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instantiation complex :: real_field
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begin
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primcorec scaleR_complex
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  where
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    "Re (scaleR r x) = r * Re x"
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  | "Im (scaleR r x) = r * Im x"
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instance
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proof
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  fix a b :: real and x y :: complex
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  show "scaleR a (x + y) = scaleR a x + scaleR a y"
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    by (simp add: complex_eq_iff distrib_left)
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  show "scaleR (a + b) x = scaleR a x + scaleR b x"
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    by (simp add: complex_eq_iff distrib_right)
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  show "scaleR a (scaleR b x) = scaleR (a * b) x"
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    by (simp add: complex_eq_iff mult.assoc)
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  show "scaleR 1 x = x"
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    by (simp add: complex_eq_iff)
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  show "scaleR a x * y = scaleR a (x * y)"
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    by (simp add: complex_eq_iff algebra_simps)
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  show "x * scaleR a y = scaleR a (x * y)"
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    by (simp add: complex_eq_iff algebra_simps)
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qed
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end
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subsection \<open>Numerals, Arithmetic, and Embedding from R\<close>
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abbreviation complex_of_real :: "real \<Rightarrow> complex"
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  where "complex_of_real \<equiv> of_real"
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declare [[coercion "of_real :: real \<Rightarrow> complex"]]
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declare [[coercion "of_rat :: rat \<Rightarrow> complex"]]
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declare [[coercion "of_int :: int \<Rightarrow> complex"]]
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declare [[coercion "of_nat :: nat \<Rightarrow> complex"]]
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lemma complex_Re_of_nat [simp]: "Re (of_nat n) = of_nat n"
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  by (induct n) simp_all
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lemma complex_Im_of_nat [simp]: "Im (of_nat n) = 0"
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  by (induct n) simp_all
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lemma complex_Re_of_int [simp]: "Re (of_int z) = of_int z"
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  by (cases z rule: int_diff_cases) simp
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lemma complex_Im_of_int [simp]: "Im (of_int z) = 0"
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  by (cases z rule: int_diff_cases) simp
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lemma complex_Re_numeral [simp]: "Re (numeral v) = numeral v"
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  using complex_Re_of_int [of "numeral v"] by simp
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lemma complex_Im_numeral [simp]: "Im (numeral v) = 0"
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  using complex_Im_of_int [of "numeral v"] by simp
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lemma Re_complex_of_real [simp]: "Re (complex_of_real z) = z"
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  by (simp add: of_real_def)
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lemma Im_complex_of_real [simp]: "Im (complex_of_real z) = 0"
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  by (simp add: of_real_def)
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lemma Re_divide_numeral [simp]: "Re (z / numeral w) = Re z / numeral w"
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  by (simp add: Re_divide sqr_conv_mult)
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lemma Im_divide_numeral [simp]: "Im (z / numeral w) = Im z / numeral w"
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  by (simp add: Im_divide sqr_conv_mult)
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lemma Re_divide_of_nat [simp]: "Re (z / of_nat n) = Re z / of_nat n"
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  by (cases n) (simp_all add: Re_divide divide_simps power2_eq_square del: of_nat_Suc)
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lemma Im_divide_of_nat [simp]: "Im (z / of_nat n) = Im z / of_nat n"
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  by (cases n) (simp_all add: Im_divide divide_simps power2_eq_square del: of_nat_Suc)
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lemma of_real_Re [simp]: "z \<in> \<real> \<Longrightarrow> of_real (Re z) = z"
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  by (auto simp: Reals_def)
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lemma complex_Re_fact [simp]: "Re (fact n) = fact n"
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proof -
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  have "(fact n :: complex) = of_real (fact n)"
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    by simp
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  also have "Re \<dots> = fact n"
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    by (subst Re_complex_of_real) simp_all
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  finally show ?thesis .
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qed
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lemma complex_Im_fact [simp]: "Im (fact n) = 0"
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  by (subst of_nat_fact [symmetric]) (simp only: complex_Im_of_nat)
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subsection \<open>The Complex Number $i$\<close>
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primcorec imaginary_unit :: complex  ("\<i>")
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  where
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    "Re \<i> = 0"
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  | "Im \<i> = 1"
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lemma Complex_eq: "Complex a b = a + \<i> * b"
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  by (simp add: complex_eq_iff)
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lemma complex_eq: "a = Re a + \<i> * Im a"
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  by (simp add: complex_eq_iff)
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lemma fun_complex_eq: "f = (\<lambda>x. Re (f x) + \<i> * Im (f x))"
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  by (simp add: fun_eq_iff complex_eq)
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lemma i_squared [simp]: "\<i> * \<i> = -1"
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  by (simp add: complex_eq_iff)
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lemma power2_i [simp]: "\<i>\<^sup>2 = -1"
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  by (simp add: power2_eq_square)
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lemma inverse_i [simp]: "inverse \<i> = - \<i>"
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  by (rule inverse_unique) simp
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lemma divide_i [simp]: "x / \<i> = - \<i> * x"
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  by (simp add: divide_complex_def)
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lemma complex_i_mult_minus [simp]: "\<i> * (\<i> * x) = - x"
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  by (simp add: mult.assoc [symmetric])
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lemma complex_i_not_zero [simp]: "\<i> \<noteq> 0"
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  by (simp add: complex_eq_iff)
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lemma complex_i_not_one [simp]: "\<i> \<noteq> 1"
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  by (simp add: complex_eq_iff)
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lemma complex_i_not_numeral [simp]: "\<i> \<noteq> numeral w"
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  by (simp add: complex_eq_iff)
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lemma complex_i_not_neg_numeral [simp]: "\<i> \<noteq> - numeral w"
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  by (simp add: complex_eq_iff)
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lemma complex_split_polar: "\<exists>r a. z = complex_of_real r * (cos a + \<i> * sin a)"
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  by (simp add: complex_eq_iff polar_Ex)
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lemma i_even_power [simp]: "\<i> ^ (n * 2) = (-1) ^ n"
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  by (metis mult.commute power2_i power_mult)
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lemma Re_i_times [simp]: "Re (\<i> * z) = - Im z"
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  by simp
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lemma Im_i_times [simp]: "Im (\<i> * z) = Re z"
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  by simp
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lemma i_times_eq_iff: "\<i> * w = z \<longleftrightarrow> w = - (\<i> * z)"
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  by auto
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lemma divide_numeral_i [simp]: "z / (numeral n * \<i>) = - (\<i> * z) / numeral n"
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  by (metis divide_divide_eq_left divide_i mult.commute mult_minus_right)
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subsection \<open>Vector Norm\<close>
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instantiation complex :: real_normed_field
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begin
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definition "norm z = sqrt ((Re z)\<^sup>2 + (Im z)\<^sup>2)"
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abbreviation cmod :: "complex \<Rightarrow> real"
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  where "cmod \<equiv> norm"
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definition complex_sgn_def: "sgn x = x /\<^sub>R cmod x"
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definition dist_complex_def: "dist x y = cmod (x - y)"
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definition uniformity_complex_def [code del]:
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  "(uniformity :: (complex \<times> complex) filter) = (INF e:{0 <..}. principal {(x, y). dist x y < e})"
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definition open_complex_def [code del]:
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  "open (U :: complex set) \<longleftrightarrow> (\<forall>x\<in>U. eventually (\<lambda>(x', y). x' = x \<longrightarrow> y \<in> U) uniformity)"
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instance
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proof
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  fix r :: real and x y :: complex and S :: "complex set"
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  show "(norm x = 0) = (x = 0)"
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    by (simp add: norm_complex_def complex_eq_iff)
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  show "norm (x + y) \<le> norm x + norm y"
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    by (simp add: norm_complex_def complex_eq_iff real_sqrt_sum_squares_triangle_ineq)
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  show "norm (scaleR r x) = \<bar>r\<bar> * norm x"
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    by (simp add: norm_complex_def complex_eq_iff power_mult_distrib distrib_left [symmetric]
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        real_sqrt_mult)
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  show "norm (x * y) = norm x * norm y"
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    by (simp add: norm_complex_def complex_eq_iff real_sqrt_mult [symmetric]
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        power2_eq_square algebra_simps)
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qed (rule complex_sgn_def dist_complex_def open_complex_def uniformity_complex_def)+
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end
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declare uniformity_Abort[where 'a = complex, code]
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lemma norm_ii [simp]: "norm \<i> = 1"
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  by (simp add: norm_complex_def)
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lemma cmod_unit_one: "cmod (cos a + \<i> * sin a) = 1"
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  by (simp add: norm_complex_def)
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lemma cmod_complex_polar: "cmod (r * (cos a + \<i> * sin a)) = \<bar>r\<bar>"
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  by (simp add: norm_mult cmod_unit_one)
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lemma complex_Re_le_cmod: "Re x \<le> cmod x"
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  unfolding norm_complex_def by (rule real_sqrt_sum_squares_ge1)
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lemma complex_mod_minus_le_complex_mod: "- cmod x \<le> cmod x"
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  by (rule order_trans [OF _ norm_ge_zero]) simp
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lemma complex_mod_triangle_ineq2: "cmod (b + a) - cmod b \<le> cmod a"
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  by (rule ord_le_eq_trans [OF norm_triangle_ineq2]) simp
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lemma abs_Re_le_cmod: "\<bar>Re x\<bar> \<le> cmod x"
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  by (simp add: norm_complex_def)
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lemma abs_Im_le_cmod: "\<bar>Im x\<bar> \<le> cmod x"
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  by (simp add: norm_complex_def)
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lemma cmod_le: "cmod z \<le> \<bar>Re z\<bar> + \<bar>Im z\<bar>"
hoelzl@57259
   329
  apply (subst complex_eq)
hoelzl@57259
   330
  apply (rule order_trans)
wenzelm@63569
   331
   apply (rule norm_triangle_ineq)
hoelzl@57259
   332
  apply (simp add: norm_mult)
hoelzl@57259
   333
  done
hoelzl@57259
   334
hoelzl@56889
   335
lemma cmod_eq_Re: "Im z = 0 \<Longrightarrow> cmod z = \<bar>Re z\<bar>"
hoelzl@56889
   336
  by (simp add: norm_complex_def)
hoelzl@56889
   337
hoelzl@56889
   338
lemma cmod_eq_Im: "Re z = 0 \<Longrightarrow> cmod z = \<bar>Im z\<bar>"
hoelzl@56889
   339
  by (simp add: norm_complex_def)
huffman@44724
   340
wenzelm@63569
   341
lemma cmod_power2: "(cmod z)\<^sup>2 = (Re z)\<^sup>2 + (Im z)\<^sup>2"
hoelzl@56889
   342
  by (simp add: norm_complex_def)
hoelzl@56889
   343
hoelzl@56889
   344
lemma cmod_plus_Re_le_0_iff: "cmod z + Re z \<le> 0 \<longleftrightarrow> Re z = - cmod z"
hoelzl@56889
   345
  using abs_Re_le_cmod[of z] by auto
hoelzl@56889
   346
wenzelm@63569
   347
lemma cmod_Re_le_iff: "Im x = Im y \<Longrightarrow> cmod x \<le> cmod y \<longleftrightarrow> \<bar>Re x\<bar> \<le> \<bar>Re y\<bar>"
lp15@62379
   348
  by (metis add.commute add_le_cancel_left norm_complex_def real_sqrt_abs real_sqrt_le_iff)
lp15@62379
   349
wenzelm@63569
   350
lemma cmod_Im_le_iff: "Re x = Re y \<Longrightarrow> cmod x \<le> cmod y \<longleftrightarrow> \<bar>Im x\<bar> \<le> \<bar>Im y\<bar>"
lp15@62379
   351
  by (metis add_le_cancel_left norm_complex_def real_sqrt_abs real_sqrt_le_iff)
lp15@62379
   352
hoelzl@56889
   353
lemma Im_eq_0: "\<bar>Re z\<bar> = cmod z \<Longrightarrow> Im z = 0"
wenzelm@63569
   354
  by (subst (asm) power_eq_iff_eq_base[symmetric, where n=2]) (auto simp add: norm_complex_def)
hoelzl@56369
   355
wenzelm@63569
   356
lemma abs_sqrt_wlog: "(\<And>x. x \<ge> 0 \<Longrightarrow> P x (x\<^sup>2)) \<Longrightarrow> P \<bar>x\<bar> (x\<^sup>2)"
wenzelm@63569
   357
  for x::"'a::linordered_idom"
wenzelm@63569
   358
  by (metis abs_ge_zero power2_abs)
hoelzl@56369
   359
hoelzl@56369
   360
lemma complex_abs_le_norm: "\<bar>Re z\<bar> + \<bar>Im z\<bar> \<le> sqrt 2 * norm z"
hoelzl@56889
   361
  unfolding norm_complex_def
hoelzl@56369
   362
  apply (rule abs_sqrt_wlog [where x="Re z"])
hoelzl@56369
   363
  apply (rule abs_sqrt_wlog [where x="Im z"])
hoelzl@56369
   364
  apply (rule power2_le_imp_le)
wenzelm@63569
   365
   apply (simp_all add: power2_sum add.commute sum_squares_bound real_sqrt_mult [symmetric])
hoelzl@56369
   366
  done
hoelzl@56369
   367
lp15@59741
   368
lemma complex_unit_circle: "z \<noteq> 0 \<Longrightarrow> (Re z / cmod z)\<^sup>2 + (Im z / cmod z)\<^sup>2 = 1"
lp15@59741
   369
  by (simp add: norm_complex_def divide_simps complex_eq_iff)
lp15@59741
   370
hoelzl@56369
   371
wenzelm@60758
   372
text \<open>Properties of complex signum.\<close>
huffman@44843
   373
huffman@44843
   374
lemma sgn_eq: "sgn z = z / complex_of_real (cmod z)"
haftmann@57512
   375
  by (simp add: sgn_div_norm divide_inverse scaleR_conv_of_real mult.commute)
huffman@44843
   376
huffman@44843
   377
lemma Re_sgn [simp]: "Re(sgn z) = Re(z)/cmod z"
huffman@44843
   378
  by (simp add: complex_sgn_def divide_inverse)
huffman@44843
   379
huffman@44843
   380
lemma Im_sgn [simp]: "Im(sgn z) = Im(z)/cmod z"
huffman@44843
   381
  by (simp add: complex_sgn_def divide_inverse)
huffman@44843
   382
paulson@14354
   383
haftmann@64290
   384
subsection \<open>Absolute value\<close>
haftmann@64290
   385
haftmann@64290
   386
instantiation complex :: field_abs_sgn
haftmann@64290
   387
begin
haftmann@64290
   388
haftmann@64290
   389
definition abs_complex :: "complex \<Rightarrow> complex"
haftmann@64290
   390
  where "abs_complex = of_real \<circ> norm"
haftmann@64290
   391
haftmann@64290
   392
instance
haftmann@64290
   393
  apply standard
haftmann@64290
   394
         apply (auto simp add: abs_complex_def complex_sgn_def norm_mult)
haftmann@64290
   395
  apply (auto simp add: scaleR_conv_of_real field_simps)
haftmann@64290
   396
  done
haftmann@64290
   397
haftmann@64290
   398
end
haftmann@64290
   399
haftmann@64290
   400
wenzelm@60758
   401
subsection \<open>Completeness of the Complexes\<close>
huffman@23123
   402
huffman@44290
   403
lemma bounded_linear_Re: "bounded_linear Re"
wenzelm@63569
   404
  by (rule bounded_linear_intro [where K=1]) (simp_all add: norm_complex_def)
huffman@44290
   405
huffman@44290
   406
lemma bounded_linear_Im: "bounded_linear Im"
wenzelm@63569
   407
  by (rule bounded_linear_intro [where K=1]) (simp_all add: norm_complex_def)
huffman@23123
   408
huffman@44290
   409
lemmas Cauchy_Re = bounded_linear.Cauchy [OF bounded_linear_Re]
huffman@44290
   410
lemmas Cauchy_Im = bounded_linear.Cauchy [OF bounded_linear_Im]
hoelzl@56381
   411
lemmas tendsto_Re [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_Re]
hoelzl@56381
   412
lemmas tendsto_Im [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_Im]
hoelzl@56381
   413
lemmas isCont_Re [simp] = bounded_linear.isCont [OF bounded_linear_Re]
hoelzl@56381
   414
lemmas isCont_Im [simp] = bounded_linear.isCont [OF bounded_linear_Im]
hoelzl@56381
   415
lemmas continuous_Re [simp] = bounded_linear.continuous [OF bounded_linear_Re]
hoelzl@56381
   416
lemmas continuous_Im [simp] = bounded_linear.continuous [OF bounded_linear_Im]
hoelzl@56381
   417
lemmas continuous_on_Re [continuous_intros] = bounded_linear.continuous_on[OF bounded_linear_Re]
hoelzl@56381
   418
lemmas continuous_on_Im [continuous_intros] = bounded_linear.continuous_on[OF bounded_linear_Im]
hoelzl@56381
   419
lemmas has_derivative_Re [derivative_intros] = bounded_linear.has_derivative[OF bounded_linear_Re]
hoelzl@56381
   420
lemmas has_derivative_Im [derivative_intros] = bounded_linear.has_derivative[OF bounded_linear_Im]
hoelzl@56381
   421
lemmas sums_Re = bounded_linear.sums [OF bounded_linear_Re]
hoelzl@56381
   422
lemmas sums_Im = bounded_linear.sums [OF bounded_linear_Im]
hoelzl@56369
   423
huffman@36825
   424
lemma tendsto_Complex [tendsto_intros]:
wenzelm@61973
   425
  "(f \<longlongrightarrow> a) F \<Longrightarrow> (g \<longlongrightarrow> b) F \<Longrightarrow> ((\<lambda>x. Complex (f x) (g x)) \<longlongrightarrow> Complex a b) F"
lp15@65274
   426
  unfolding Complex_eq by (auto intro!: tendsto_intros)
hoelzl@56369
   427
hoelzl@56369
   428
lemma tendsto_complex_iff:
wenzelm@61973
   429
  "(f \<longlongrightarrow> x) F \<longleftrightarrow> (((\<lambda>x. Re (f x)) \<longlongrightarrow> Re x) F \<and> ((\<lambda>x. Im (f x)) \<longlongrightarrow> Im x) F)"
hoelzl@56889
   430
proof safe
wenzelm@61973
   431
  assume "((\<lambda>x. Re (f x)) \<longlongrightarrow> Re x) F" "((\<lambda>x. Im (f x)) \<longlongrightarrow> Im x) F"
wenzelm@61973
   432
  from tendsto_Complex[OF this] show "(f \<longlongrightarrow> x) F"
hoelzl@56889
   433
    unfolding complex.collapse .
hoelzl@56889
   434
qed (auto intro: tendsto_intros)
hoelzl@56369
   435
wenzelm@63569
   436
lemma continuous_complex_iff:
wenzelm@63569
   437
  "continuous F f \<longleftrightarrow> continuous F (\<lambda>x. Re (f x)) \<and> continuous F (\<lambda>x. Im (f x))"
wenzelm@63569
   438
  by (simp only: continuous_def tendsto_complex_iff)
hoelzl@57259
   439
lp15@64773
   440
lemma continuous_on_of_real_o_iff [simp]:
lp15@64773
   441
     "continuous_on S (\<lambda>x. complex_of_real (g x)) = continuous_on S g"
lp15@64773
   442
  using continuous_on_Re continuous_on_of_real  by fastforce
lp15@64773
   443
lp15@64773
   444
lemma continuous_on_of_real_id [simp]:
lp15@64773
   445
     "continuous_on S (of_real :: real \<Rightarrow> 'a::real_normed_algebra_1)"
lp15@64773
   446
  by (rule continuous_on_of_real [OF continuous_on_id])
lp15@64773
   447
hoelzl@57259
   448
lemma has_vector_derivative_complex_iff: "(f has_vector_derivative x) F \<longleftrightarrow>
hoelzl@57259
   449
    ((\<lambda>x. Re (f x)) has_field_derivative (Re x)) F \<and>
hoelzl@57259
   450
    ((\<lambda>x. Im (f x)) has_field_derivative (Im x)) F"
wenzelm@63569
   451
  by (simp add: has_vector_derivative_def has_field_derivative_def has_derivative_def
wenzelm@63569
   452
      tendsto_complex_iff field_simps bounded_linear_scaleR_left bounded_linear_mult_right)
hoelzl@57259
   453
hoelzl@57259
   454
lemma has_field_derivative_Re[derivative_intros]:
hoelzl@57259
   455
  "(f has_vector_derivative D) F \<Longrightarrow> ((\<lambda>x. Re (f x)) has_field_derivative (Re D)) F"
hoelzl@57259
   456
  unfolding has_vector_derivative_complex_iff by safe
hoelzl@57259
   457
hoelzl@57259
   458
lemma has_field_derivative_Im[derivative_intros]:
hoelzl@57259
   459
  "(f has_vector_derivative D) F \<Longrightarrow> ((\<lambda>x. Im (f x)) has_field_derivative (Im D)) F"
hoelzl@57259
   460
  unfolding has_vector_derivative_complex_iff by safe
hoelzl@57259
   461
huffman@23123
   462
instance complex :: banach
huffman@23123
   463
proof
huffman@23123
   464
  fix X :: "nat \<Rightarrow> complex"
huffman@23123
   465
  assume X: "Cauchy X"
wenzelm@63569
   466
  then have "(\<lambda>n. Complex (Re (X n)) (Im (X n))) \<longlonglongrightarrow>
wenzelm@63569
   467
    Complex (lim (\<lambda>n. Re (X n))) (lim (\<lambda>n. Im (X n)))"
wenzelm@63569
   468
    by (intro tendsto_Complex convergent_LIMSEQ_iff[THEN iffD1]
wenzelm@63569
   469
        Cauchy_convergent_iff[THEN iffD1] Cauchy_Re Cauchy_Im)
hoelzl@56889
   470
  then show "convergent X"
hoelzl@56889
   471
    unfolding complex.collapse by (rule convergentI)
huffman@23123
   472
qed
huffman@23123
   473
wenzelm@63569
   474
declare DERIV_power[where 'a=complex, unfolded of_nat_def[symmetric], derivative_intros]
wenzelm@63569
   475
lp15@56238
   476
wenzelm@60758
   477
subsection \<open>Complex Conjugation\<close>
huffman@23125
   478
wenzelm@63569
   479
primcorec cnj :: "complex \<Rightarrow> complex"
wenzelm@63569
   480
  where
wenzelm@63569
   481
    "Re (cnj z) = Re z"
wenzelm@63569
   482
  | "Im (cnj z) = - Im z"
huffman@23125
   483
wenzelm@63569
   484
lemma complex_cnj_cancel_iff [simp]: "cnj x = cnj y \<longleftrightarrow> x = y"
huffman@44724
   485
  by (simp add: complex_eq_iff)
huffman@23125
   486
huffman@23125
   487
lemma complex_cnj_cnj [simp]: "cnj (cnj z) = z"
hoelzl@56889
   488
  by (simp add: complex_eq_iff)
huffman@23125
   489
huffman@23125
   490
lemma complex_cnj_zero [simp]: "cnj 0 = 0"
huffman@44724
   491
  by (simp add: complex_eq_iff)
huffman@23125
   492
wenzelm@63569
   493
lemma complex_cnj_zero_iff [iff]: "cnj z = 0 \<longleftrightarrow> z = 0"
huffman@44724
   494
  by (simp add: complex_eq_iff)
huffman@23125
   495
hoelzl@56889
   496
lemma complex_cnj_add [simp]: "cnj (x + y) = cnj x + cnj y"
huffman@44724
   497
  by (simp add: complex_eq_iff)
huffman@23125
   498
nipkow@64267
   499
lemma cnj_sum [simp]: "cnj (sum f s) = (\<Sum>x\<in>s. cnj (f x))"
hoelzl@56889
   500
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   501
hoelzl@56889
   502
lemma complex_cnj_diff [simp]: "cnj (x - y) = cnj x - cnj y"
huffman@44724
   503
  by (simp add: complex_eq_iff)
huffman@23125
   504
hoelzl@56889
   505
lemma complex_cnj_minus [simp]: "cnj (- x) = - cnj x"
huffman@44724
   506
  by (simp add: complex_eq_iff)
huffman@23125
   507
huffman@23125
   508
lemma complex_cnj_one [simp]: "cnj 1 = 1"
huffman@44724
   509
  by (simp add: complex_eq_iff)
huffman@23125
   510
hoelzl@56889
   511
lemma complex_cnj_mult [simp]: "cnj (x * y) = cnj x * cnj y"
huffman@44724
   512
  by (simp add: complex_eq_iff)
huffman@23125
   513
nipkow@64272
   514
lemma cnj_prod [simp]: "cnj (prod f s) = (\<Prod>x\<in>s. cnj (f x))"
hoelzl@56889
   515
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   516
hoelzl@56889
   517
lemma complex_cnj_inverse [simp]: "cnj (inverse x) = inverse (cnj x)"
hoelzl@56889
   518
  by (simp add: complex_eq_iff)
paulson@14323
   519
hoelzl@56889
   520
lemma complex_cnj_divide [simp]: "cnj (x / y) = cnj x / cnj y"
hoelzl@56889
   521
  by (simp add: divide_complex_def)
huffman@23125
   522
hoelzl@56889
   523
lemma complex_cnj_power [simp]: "cnj (x ^ n) = cnj x ^ n"
hoelzl@56889
   524
  by (induct n) simp_all
huffman@23125
   525
huffman@23125
   526
lemma complex_cnj_of_nat [simp]: "cnj (of_nat n) = of_nat n"
huffman@44724
   527
  by (simp add: complex_eq_iff)
huffman@23125
   528
huffman@23125
   529
lemma complex_cnj_of_int [simp]: "cnj (of_int z) = of_int z"
huffman@44724
   530
  by (simp add: complex_eq_iff)
huffman@23125
   531
huffman@47108
   532
lemma complex_cnj_numeral [simp]: "cnj (numeral w) = numeral w"
huffman@47108
   533
  by (simp add: complex_eq_iff)
huffman@47108
   534
haftmann@54489
   535
lemma complex_cnj_neg_numeral [simp]: "cnj (- numeral w) = - numeral w"
huffman@44724
   536
  by (simp add: complex_eq_iff)
huffman@23125
   537
hoelzl@56889
   538
lemma complex_cnj_scaleR [simp]: "cnj (scaleR r x) = scaleR r (cnj x)"
huffman@44724
   539
  by (simp add: complex_eq_iff)
huffman@23125
   540
huffman@23125
   541
lemma complex_mod_cnj [simp]: "cmod (cnj z) = cmod z"
hoelzl@56889
   542
  by (simp add: norm_complex_def)
paulson@14323
   543
huffman@23125
   544
lemma complex_cnj_complex_of_real [simp]: "cnj (of_real x) = of_real x"
huffman@44724
   545
  by (simp add: complex_eq_iff)
huffman@23125
   546
wenzelm@63569
   547
lemma complex_cnj_i [simp]: "cnj \<i> = - \<i>"
huffman@44724
   548
  by (simp add: complex_eq_iff)
huffman@23125
   549
huffman@23125
   550
lemma complex_add_cnj: "z + cnj z = complex_of_real (2 * Re z)"
huffman@44724
   551
  by (simp add: complex_eq_iff)
huffman@23125
   552
wenzelm@63569
   553
lemma complex_diff_cnj: "z - cnj z = complex_of_real (2 * Im z) * \<i>"
huffman@44724
   554
  by (simp add: complex_eq_iff)
paulson@14354
   555
wenzelm@53015
   556
lemma complex_mult_cnj: "z * cnj z = complex_of_real ((Re z)\<^sup>2 + (Im z)\<^sup>2)"
huffman@44724
   557
  by (simp add: complex_eq_iff power2_eq_square)
huffman@23125
   558
wenzelm@53015
   559
lemma complex_mod_mult_cnj: "cmod (z * cnj z) = (cmod z)\<^sup>2"
huffman@44724
   560
  by (simp add: norm_mult power2_eq_square)
huffman@23125
   561
huffman@44827
   562
lemma complex_mod_sqrt_Re_mult_cnj: "cmod z = sqrt (Re (z * cnj z))"
hoelzl@56889
   563
  by (simp add: norm_complex_def power2_eq_square)
huffman@44827
   564
huffman@44827
   565
lemma complex_In_mult_cnj_zero [simp]: "Im (z * cnj z) = 0"
huffman@44827
   566
  by simp
huffman@44827
   567
eberlm@61531
   568
lemma complex_cnj_fact [simp]: "cnj (fact n) = fact n"
eberlm@61531
   569
  by (subst of_nat_fact [symmetric], subst complex_cnj_of_nat) simp
eberlm@61531
   570
eberlm@61531
   571
lemma complex_cnj_pochhammer [simp]: "cnj (pochhammer z n) = pochhammer (cnj z) n"
wenzelm@63569
   572
  by (induct n arbitrary: z) (simp_all add: pochhammer_rec)
eberlm@61531
   573
huffman@44290
   574
lemma bounded_linear_cnj: "bounded_linear cnj"
wenzelm@63569
   575
  using complex_cnj_add complex_cnj_scaleR by (rule bounded_linear_intro [where K=1]) simp
paulson@14354
   576
hoelzl@56381
   577
lemmas tendsto_cnj [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_cnj]
wenzelm@63569
   578
  and isCont_cnj [simp] = bounded_linear.isCont [OF bounded_linear_cnj]
wenzelm@63569
   579
  and continuous_cnj [simp, continuous_intros] = bounded_linear.continuous [OF bounded_linear_cnj]
wenzelm@63569
   580
  and continuous_on_cnj [simp, continuous_intros] = bounded_linear.continuous_on [OF bounded_linear_cnj]
wenzelm@63569
   581
  and has_derivative_cnj [simp, derivative_intros] = bounded_linear.has_derivative [OF bounded_linear_cnj]
huffman@44290
   582
wenzelm@61973
   583
lemma lim_cnj: "((\<lambda>x. cnj(f x)) \<longlongrightarrow> cnj l) F \<longleftrightarrow> (f \<longlongrightarrow> l) F"
hoelzl@56889
   584
  by (simp add: tendsto_iff dist_complex_def complex_cnj_diff [symmetric] del: complex_cnj_diff)
hoelzl@56369
   585
hoelzl@56369
   586
lemma sums_cnj: "((\<lambda>x. cnj(f x)) sums cnj l) \<longleftrightarrow> (f sums l)"
nipkow@64267
   587
  by (simp add: sums_def lim_cnj cnj_sum [symmetric] del: cnj_sum)
hoelzl@56369
   588
paulson@14354
   589
wenzelm@63569
   590
subsection \<open>Basic Lemmas\<close>
lp15@55734
   591
lp15@55734
   592
lemma complex_eq_0: "z=0 \<longleftrightarrow> (Re z)\<^sup>2 + (Im z)\<^sup>2 = 0"
hoelzl@56889
   593
  by (metis zero_complex.sel complex_eqI sum_power2_eq_zero_iff)
lp15@55734
   594
lp15@55734
   595
lemma complex_neq_0: "z\<noteq>0 \<longleftrightarrow> (Re z)\<^sup>2 + (Im z)\<^sup>2 > 0"
hoelzl@56889
   596
  by (metis complex_eq_0 less_numeral_extra(3) sum_power2_gt_zero_iff)
lp15@55734
   597
lp15@55734
   598
lemma complex_norm_square: "of_real ((norm z)\<^sup>2) = z * cnj z"
wenzelm@63569
   599
  by (cases z)
wenzelm@63569
   600
    (auto simp: complex_eq_iff norm_complex_def power2_eq_square[symmetric] of_real_power[symmetric]
wenzelm@63569
   601
      simp del: of_real_power)
lp15@55734
   602
wenzelm@63569
   603
lemma complex_div_cnj: "a / b = (a * cnj b) / (norm b)\<^sup>2"
paulson@61104
   604
  using complex_norm_square by auto
paulson@61104
   605
lp15@59741
   606
lemma Re_complex_div_eq_0: "Re (a / b) = 0 \<longleftrightarrow> Re (a * cnj b) = 0"
hoelzl@56889
   607
  by (auto simp add: Re_divide)
lp15@59613
   608
lp15@59741
   609
lemma Im_complex_div_eq_0: "Im (a / b) = 0 \<longleftrightarrow> Im (a * cnj b) = 0"
hoelzl@56889
   610
  by (auto simp add: Im_divide)
hoelzl@56889
   611
wenzelm@63569
   612
lemma complex_div_gt_0: "(Re (a / b) > 0 \<longleftrightarrow> Re (a * cnj b) > 0) \<and> (Im (a / b) > 0 \<longleftrightarrow> Im (a * cnj b) > 0)"
wenzelm@63569
   613
proof (cases "b = 0")
wenzelm@63569
   614
  case True
wenzelm@63569
   615
  then show ?thesis by auto
lp15@55734
   616
next
wenzelm@63569
   617
  case False
hoelzl@56889
   618
  then have "0 < (Re b)\<^sup>2 + (Im b)\<^sup>2"
hoelzl@56889
   619
    by (simp add: complex_eq_iff sum_power2_gt_zero_iff)
hoelzl@56889
   620
  then show ?thesis
hoelzl@56889
   621
    by (simp add: Re_divide Im_divide zero_less_divide_iff)
lp15@55734
   622
qed
lp15@55734
   623
lp15@59741
   624
lemma Re_complex_div_gt_0: "Re (a / b) > 0 \<longleftrightarrow> Re (a * cnj b) > 0"
lp15@59741
   625
  and Im_complex_div_gt_0: "Im (a / b) > 0 \<longleftrightarrow> Im (a * cnj b) > 0"
hoelzl@56889
   626
  using complex_div_gt_0 by auto
lp15@55734
   627
wenzelm@63569
   628
lemma Re_complex_div_ge_0: "Re (a / b) \<ge> 0 \<longleftrightarrow> Re (a * cnj b) \<ge> 0"
lp15@59741
   629
  by (metis le_less Re_complex_div_eq_0 Re_complex_div_gt_0)
lp15@55734
   630
wenzelm@63569
   631
lemma Im_complex_div_ge_0: "Im (a / b) \<ge> 0 \<longleftrightarrow> Im (a * cnj b) \<ge> 0"
lp15@59741
   632
  by (metis Im_complex_div_eq_0 Im_complex_div_gt_0 le_less)
lp15@55734
   633
wenzelm@63569
   634
lemma Re_complex_div_lt_0: "Re (a / b) < 0 \<longleftrightarrow> Re (a * cnj b) < 0"
lp15@59741
   635
  by (metis less_asym neq_iff Re_complex_div_eq_0 Re_complex_div_gt_0)
lp15@55734
   636
wenzelm@63569
   637
lemma Im_complex_div_lt_0: "Im (a / b) < 0 \<longleftrightarrow> Im (a * cnj b) < 0"
lp15@59741
   638
  by (metis Im_complex_div_eq_0 Im_complex_div_gt_0 less_asym neq_iff)
lp15@55734
   639
wenzelm@63569
   640
lemma Re_complex_div_le_0: "Re (a / b) \<le> 0 \<longleftrightarrow> Re (a * cnj b) \<le> 0"
lp15@59741
   641
  by (metis not_le Re_complex_div_gt_0)
lp15@55734
   642
wenzelm@63569
   643
lemma Im_complex_div_le_0: "Im (a / b) \<le> 0 \<longleftrightarrow> Im (a * cnj b) \<le> 0"
lp15@59741
   644
  by (metis Im_complex_div_gt_0 not_le)
lp15@55734
   645
paulson@61104
   646
lemma Re_divide_of_real [simp]: "Re (z / of_real r) = Re z / r"
paulson@61104
   647
  by (simp add: Re_divide power2_eq_square)
paulson@61104
   648
paulson@61104
   649
lemma Im_divide_of_real [simp]: "Im (z / of_real r) = Im z / r"
paulson@61104
   650
  by (simp add: Im_divide power2_eq_square)
paulson@61104
   651
lp15@65578
   652
lemma Re_divide_Reals [simp]: "r \<in> \<real> \<Longrightarrow> Re (z / r) = Re z / Re r"
paulson@61104
   653
  by (metis Re_divide_of_real of_real_Re)
paulson@61104
   654
lp15@65578
   655
lemma Im_divide_Reals [simp]: "r \<in> \<real> \<Longrightarrow> Im (z / r) = Im z / Re r"
paulson@61104
   656
  by (metis Im_divide_of_real of_real_Re)
paulson@61104
   657
nipkow@64267
   658
lemma Re_sum[simp]: "Re (sum f s) = (\<Sum>x\<in>s. Re (f x))"
hoelzl@56369
   659
  by (induct s rule: infinite_finite_induct) auto
lp15@55734
   660
nipkow@64267
   661
lemma Im_sum[simp]: "Im (sum f s) = (\<Sum>x\<in>s. Im(f x))"
hoelzl@56369
   662
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   663
hoelzl@56369
   664
lemma sums_complex_iff: "f sums x \<longleftrightarrow> ((\<lambda>x. Re (f x)) sums Re x) \<and> ((\<lambda>x. Im (f x)) sums Im x)"
nipkow@64267
   665
  unfolding sums_def tendsto_complex_iff Im_sum Re_sum ..
lp15@59613
   666
hoelzl@56369
   667
lemma summable_complex_iff: "summable f \<longleftrightarrow> summable (\<lambda>x. Re (f x)) \<and>  summable (\<lambda>x. Im (f x))"
hoelzl@56889
   668
  unfolding summable_def sums_complex_iff[abs_def] by (metis complex.sel)
hoelzl@56369
   669
hoelzl@56369
   670
lemma summable_complex_of_real [simp]: "summable (\<lambda>n. complex_of_real (f n)) \<longleftrightarrow> summable f"
hoelzl@56369
   671
  unfolding summable_complex_iff by simp
hoelzl@56369
   672
hoelzl@56369
   673
lemma summable_Re: "summable f \<Longrightarrow> summable (\<lambda>x. Re (f x))"
hoelzl@56369
   674
  unfolding summable_complex_iff by blast
hoelzl@56369
   675
hoelzl@56369
   676
lemma summable_Im: "summable f \<Longrightarrow> summable (\<lambda>x. Im (f x))"
hoelzl@56369
   677
  unfolding summable_complex_iff by blast
lp15@56217
   678
paulson@61104
   679
lemma complex_is_Nat_iff: "z \<in> \<nat> \<longleftrightarrow> Im z = 0 \<and> (\<exists>i. Re z = of_nat i)"
paulson@61104
   680
  by (auto simp: Nats_def complex_eq_iff)
paulson@61104
   681
paulson@61104
   682
lemma complex_is_Int_iff: "z \<in> \<int> \<longleftrightarrow> Im z = 0 \<and> (\<exists>i. Re z = of_int i)"
paulson@61104
   683
  by (auto simp: Ints_def complex_eq_iff)
paulson@61104
   684
hoelzl@56889
   685
lemma complex_is_Real_iff: "z \<in> \<real> \<longleftrightarrow> Im z = 0"
hoelzl@56889
   686
  by (auto simp: Reals_def complex_eq_iff)
lp15@55734
   687
lp15@55734
   688
lemma Reals_cnj_iff: "z \<in> \<real> \<longleftrightarrow> cnj z = z"
hoelzl@56889
   689
  by (auto simp: complex_is_Real_iff complex_eq_iff)
lp15@55734
   690
wenzelm@61944
   691
lemma in_Reals_norm: "z \<in> \<real> \<Longrightarrow> norm z = \<bar>Re z\<bar>"
hoelzl@56889
   692
  by (simp add: complex_is_Real_iff norm_complex_def)
hoelzl@56369
   693
lp15@65578
   694
lemma Re_Reals_divide: "r \<in> \<real> \<Longrightarrow> Re (r / z) = Re r * Re z / (norm z)\<^sup>2"
lp15@65578
   695
  by (simp add: Re_divide complex_is_Real_iff cmod_power2)
lp15@65578
   696
lp15@65578
   697
lemma Im_Reals_divide: "r \<in> \<real> \<Longrightarrow> Im (r / z) = -Re r * Im z / (norm z)\<^sup>2"
lp15@65578
   698
  by (simp add: Im_divide complex_is_Real_iff cmod_power2)
lp15@65578
   699
hoelzl@56369
   700
lemma series_comparison_complex:
hoelzl@56369
   701
  fixes f:: "nat \<Rightarrow> 'a::banach"
hoelzl@56369
   702
  assumes sg: "summable g"
wenzelm@63569
   703
    and "\<And>n. g n \<in> \<real>" "\<And>n. Re (g n) \<ge> 0"
wenzelm@63569
   704
    and fg: "\<And>n. n \<ge> N \<Longrightarrow> norm(f n) \<le> norm(g n)"
hoelzl@56369
   705
  shows "summable f"
hoelzl@56369
   706
proof -
wenzelm@63569
   707
  have g: "\<And>n. cmod (g n) = Re (g n)"
wenzelm@63569
   708
    using assms by (metis abs_of_nonneg in_Reals_norm)
hoelzl@56369
   709
  show ?thesis
hoelzl@56369
   710
    apply (rule summable_comparison_test' [where g = "\<lambda>n. norm (g n)" and N=N])
hoelzl@56369
   711
    using sg
wenzelm@63569
   712
     apply (auto simp: summable_def)
wenzelm@63569
   713
     apply (rule_tac x = "Re s" in exI)
wenzelm@63569
   714
     apply (auto simp: g sums_Re)
hoelzl@56369
   715
    apply (metis fg g)
hoelzl@56369
   716
    done
hoelzl@56369
   717
qed
lp15@55734
   718
wenzelm@63569
   719
wenzelm@63569
   720
subsection \<open>Polar Form for Complex Numbers\<close>
lp15@59746
   721
lp15@62620
   722
lemma complex_unimodular_polar:
wenzelm@63569
   723
  assumes "norm z = 1"
wenzelm@63569
   724
  obtains t where "0 \<le> t" "t < 2 * pi" "z = Complex (cos t) (sin t)"
wenzelm@63569
   725
  by (metis cmod_power2 one_power2 complex_surj sincos_total_2pi [of "Re z" "Im z"] assms)
wenzelm@63569
   726
paulson@14323
   727
wenzelm@60758
   728
subsubsection \<open>$\cos \theta + i \sin \theta$\<close>
huffman@20557
   729
wenzelm@63569
   730
primcorec cis :: "real \<Rightarrow> complex"
wenzelm@63569
   731
  where
wenzelm@63569
   732
    "Re (cis a) = cos a"
wenzelm@63569
   733
  | "Im (cis a) = sin a"
huffman@44827
   734
huffman@44827
   735
lemma cis_zero [simp]: "cis 0 = 1"
hoelzl@56889
   736
  by (simp add: complex_eq_iff)
huffman@44827
   737
huffman@44828
   738
lemma norm_cis [simp]: "norm (cis a) = 1"
hoelzl@56889
   739
  by (simp add: norm_complex_def)
huffman@44828
   740
huffman@44828
   741
lemma sgn_cis [simp]: "sgn (cis a) = cis a"
huffman@44828
   742
  by (simp add: sgn_div_norm)
huffman@44828
   743
huffman@44828
   744
lemma cis_neq_zero [simp]: "cis a \<noteq> 0"
huffman@44828
   745
  by (metis norm_cis norm_zero zero_neq_one)
huffman@44828
   746
huffman@44827
   747
lemma cis_mult: "cis a * cis b = cis (a + b)"
hoelzl@56889
   748
  by (simp add: complex_eq_iff cos_add sin_add)
huffman@44827
   749
huffman@44827
   750
lemma DeMoivre: "(cis a) ^ n = cis (real n * a)"
wenzelm@63569
   751
  by (induct n) (simp_all add: algebra_simps cis_mult)
huffman@44827
   752
wenzelm@63569
   753
lemma cis_inverse [simp]: "inverse (cis a) = cis (- a)"
hoelzl@56889
   754
  by (simp add: complex_eq_iff)
huffman@44827
   755
huffman@44827
   756
lemma cis_divide: "cis a / cis b = cis (a - b)"
hoelzl@56889
   757
  by (simp add: divide_complex_def cis_mult)
huffman@44827
   758
wenzelm@63569
   759
lemma cos_n_Re_cis_pow_n: "cos (real n * a) = Re (cis a ^ n)"
huffman@44827
   760
  by (auto simp add: DeMoivre)
huffman@44827
   761
wenzelm@63569
   762
lemma sin_n_Im_cis_pow_n: "sin (real n * a) = Im (cis a ^ n)"
huffman@44827
   763
  by (auto simp add: DeMoivre)
huffman@44827
   764
hoelzl@56889
   765
lemma cis_pi: "cis pi = -1"
hoelzl@56889
   766
  by (simp add: complex_eq_iff)
hoelzl@56889
   767
wenzelm@63569
   768
wenzelm@60758
   769
subsubsection \<open>$r(\cos \theta + i \sin \theta)$\<close>
huffman@44715
   770
wenzelm@63569
   771
definition rcis :: "real \<Rightarrow> real \<Rightarrow> complex"
wenzelm@63569
   772
  where "rcis r a = complex_of_real r * cis a"
huffman@20557
   773
huffman@44827
   774
lemma Re_rcis [simp]: "Re(rcis r a) = r * cos a"
huffman@44828
   775
  by (simp add: rcis_def)
huffman@44827
   776
huffman@44827
   777
lemma Im_rcis [simp]: "Im(rcis r a) = r * sin a"
huffman@44828
   778
  by (simp add: rcis_def)
huffman@44827
   779
huffman@44827
   780
lemma rcis_Ex: "\<exists>r a. z = rcis r a"
huffman@44828
   781
  by (simp add: complex_eq_iff polar_Ex)
huffman@44827
   782
wenzelm@61944
   783
lemma complex_mod_rcis [simp]: "cmod (rcis r a) = \<bar>r\<bar>"
huffman@44828
   784
  by (simp add: rcis_def norm_mult)
huffman@44827
   785
huffman@44827
   786
lemma cis_rcis_eq: "cis a = rcis 1 a"
huffman@44827
   787
  by (simp add: rcis_def)
huffman@44827
   788
wenzelm@63569
   789
lemma rcis_mult: "rcis r1 a * rcis r2 b = rcis (r1 * r2) (a + b)"
huffman@44828
   790
  by (simp add: rcis_def cis_mult)
huffman@44827
   791
huffman@44827
   792
lemma rcis_zero_mod [simp]: "rcis 0 a = 0"
huffman@44827
   793
  by (simp add: rcis_def)
huffman@44827
   794
huffman@44827
   795
lemma rcis_zero_arg [simp]: "rcis r 0 = complex_of_real r"
huffman@44827
   796
  by (simp add: rcis_def)
huffman@44827
   797
huffman@44828
   798
lemma rcis_eq_zero_iff [simp]: "rcis r a = 0 \<longleftrightarrow> r = 0"
huffman@44828
   799
  by (simp add: rcis_def)
huffman@44828
   800
huffman@44827
   801
lemma DeMoivre2: "(rcis r a) ^ n = rcis (r ^ n) (real n * a)"
huffman@44827
   802
  by (simp add: rcis_def power_mult_distrib DeMoivre)
huffman@44827
   803
wenzelm@63569
   804
lemma rcis_inverse: "inverse(rcis r a) = rcis (1 / r) (- a)"
huffman@44827
   805
  by (simp add: divide_inverse rcis_def)
huffman@44827
   806
wenzelm@63569
   807
lemma rcis_divide: "rcis r1 a / rcis r2 b = rcis (r1 / r2) (a - b)"
huffman@44828
   808
  by (simp add: rcis_def cis_divide [symmetric])
huffman@44827
   809
wenzelm@63569
   810
wenzelm@60758
   811
subsubsection \<open>Complex exponential\<close>
huffman@44827
   812
hoelzl@56889
   813
lemma cis_conv_exp: "cis b = exp (\<i> * b)"
hoelzl@56889
   814
proof -
wenzelm@63569
   815
  have "(\<i> * complex_of_real b) ^ n /\<^sub>R fact n =
wenzelm@63569
   816
      of_real (cos_coeff n * b^n) + \<i> * of_real (sin_coeff n * b^n)"
wenzelm@63569
   817
    for n :: nat
wenzelm@63569
   818
  proof -
hoelzl@56889
   819
    have "\<i> ^ n = fact n *\<^sub>R (cos_coeff n + \<i> * sin_coeff n)"
hoelzl@56889
   820
      by (induct n)
wenzelm@63569
   821
        (simp_all add: sin_coeff_Suc cos_coeff_Suc complex_eq_iff Re_divide Im_divide field_simps
wenzelm@63569
   822
          power2_eq_square add_nonneg_eq_0_iff)
wenzelm@63569
   823
    then show ?thesis
wenzelm@63569
   824
      by (simp add: field_simps)
wenzelm@63569
   825
  qed
wenzelm@63569
   826
  then show ?thesis
wenzelm@63569
   827
    using sin_converges [of b] cos_converges [of b]
lp15@65274
   828
    by (auto simp add: Complex_eq cis.ctr exp_def simp del: of_real_mult
wenzelm@63569
   829
        intro!: sums_unique sums_add sums_mult sums_of_real)
huffman@44291
   830
qed
huffman@44291
   831
lp15@61762
   832
lemma exp_eq_polar: "exp z = exp (Re z) * cis (Im z)"
wenzelm@63569
   833
  unfolding cis_conv_exp exp_of_real [symmetric] mult_exp_exp
lp15@65274
   834
  by (cases z) (simp add: Complex_eq)
huffman@20557
   835
huffman@44828
   836
lemma Re_exp: "Re (exp z) = exp (Re z) * cos (Im z)"
lp15@61762
   837
  unfolding exp_eq_polar by simp
huffman@44828
   838
huffman@44828
   839
lemma Im_exp: "Im (exp z) = exp (Re z) * sin (Im z)"
lp15@61762
   840
  unfolding exp_eq_polar by simp
huffman@44828
   841
lp15@59746
   842
lemma norm_cos_sin [simp]: "norm (Complex (cos t) (sin t)) = 1"
lp15@59746
   843
  by (simp add: norm_complex_def)
lp15@59746
   844
lp15@59746
   845
lemma norm_exp_eq_Re [simp]: "norm (exp z) = exp (Re z)"
lp15@65274
   846
  by (simp add: cis.code cmod_complex_polar exp_eq_polar Complex_eq)
lp15@59746
   847
lp15@61762
   848
lemma complex_exp_exists: "\<exists>a r. z = complex_of_real r * exp a"
lp15@59746
   849
  apply (insert rcis_Ex [of z])
lp15@61762
   850
  apply (auto simp add: exp_eq_polar rcis_def mult.assoc [symmetric])
wenzelm@63569
   851
  apply (rule_tac x = "\<i> * complex_of_real a" in exI)
wenzelm@63569
   852
  apply auto
lp15@59746
   853
  done
paulson@14323
   854
wenzelm@63569
   855
lemma exp_pi_i [simp]: "exp (of_real pi * \<i>) = -1"
lp15@61848
   856
  by (metis cis_conv_exp cis_pi mult.commute)
lp15@61848
   857
wenzelm@63569
   858
lemma exp_pi_i' [simp]: "exp (\<i> * of_real pi) = -1"
lp15@63114
   859
  using cis_conv_exp cis_pi by auto
lp15@63114
   860
wenzelm@63569
   861
lemma exp_two_pi_i [simp]: "exp (2 * of_real pi * \<i>) = 1"
lp15@61762
   862
  by (simp add: exp_eq_polar complex_eq_iff)
paulson@14387
   863
lp15@63114
   864
lemma exp_two_pi_i' [simp]: "exp (\<i> * (of_real pi * 2)) = 1"
lp15@63114
   865
  by (metis exp_two_pi_i mult.commute)
lp15@63114
   866
wenzelm@63569
   867
wenzelm@60758
   868
subsubsection \<open>Complex argument\<close>
huffman@44844
   869
wenzelm@63569
   870
definition arg :: "complex \<Rightarrow> real"
wenzelm@63569
   871
  where "arg z = (if z = 0 then 0 else (SOME a. sgn z = cis a \<and> - pi < a \<and> a \<le> pi))"
huffman@44844
   872
huffman@44844
   873
lemma arg_zero: "arg 0 = 0"
huffman@44844
   874
  by (simp add: arg_def)
huffman@44844
   875
huffman@44844
   876
lemma arg_unique:
huffman@44844
   877
  assumes "sgn z = cis x" and "-pi < x" and "x \<le> pi"
huffman@44844
   878
  shows "arg z = x"
huffman@44844
   879
proof -
huffman@44844
   880
  from assms have "z \<noteq> 0" by auto
huffman@44844
   881
  have "(SOME a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi) = x"
huffman@44844
   882
  proof
wenzelm@63040
   883
    fix a
wenzelm@63040
   884
    define d where "d = a - x"
huffman@44844
   885
    assume a: "sgn z = cis a \<and> - pi < a \<and> a \<le> pi"
huffman@44844
   886
    from a assms have "- (2*pi) < d \<and> d < 2*pi"
huffman@44844
   887
      unfolding d_def by simp
wenzelm@63569
   888
    moreover
wenzelm@63569
   889
    from a assms have "cos a = cos x" and "sin a = sin x"
huffman@44844
   890
      by (simp_all add: complex_eq_iff)
wenzelm@63569
   891
    then have cos: "cos d = 1"
wenzelm@63569
   892
      by (simp add: d_def cos_diff)
wenzelm@63569
   893
    moreover from cos have "sin d = 0"
wenzelm@63569
   894
      by (rule cos_one_sin_zero)
huffman@44844
   895
    ultimately have "d = 0"
wenzelm@63569
   896
      by (auto simp: sin_zero_iff elim!: evenE dest!: less_2_cases)
wenzelm@63569
   897
    then show "a = x"
wenzelm@63569
   898
      by (simp add: d_def)
huffman@44844
   899
  qed (simp add: assms del: Re_sgn Im_sgn)
wenzelm@60758
   900
  with \<open>z \<noteq> 0\<close> show "arg z = x"
wenzelm@63569
   901
    by (simp add: arg_def)
huffman@44844
   902
qed
huffman@44844
   903
huffman@44844
   904
lemma arg_correct:
wenzelm@63569
   905
  assumes "z \<noteq> 0"
wenzelm@63569
   906
  shows "sgn z = cis (arg z) \<and> -pi < arg z \<and> arg z \<le> pi"
huffman@44844
   907
proof (simp add: arg_def assms, rule someI_ex)
wenzelm@63569
   908
  obtain r a where z: "z = rcis r a"
wenzelm@63569
   909
    using rcis_Ex by fast
huffman@44844
   910
  with assms have "r \<noteq> 0" by auto
wenzelm@63040
   911
  define b where "b = (if 0 < r then a else a + pi)"
huffman@44844
   912
  have b: "sgn z = cis b"
wenzelm@63569
   913
    using \<open>r \<noteq> 0\<close> by (simp add: z b_def rcis_def of_real_def sgn_scaleR sgn_if complex_eq_iff)
wenzelm@63569
   914
  have cis_2pi_nat: "cis (2 * pi * real_of_nat n) = 1" for n
wenzelm@63569
   915
    by (induct n) (simp_all add: distrib_left cis_mult [symmetric] complex_eq_iff)
wenzelm@63569
   916
  have cis_2pi_int: "cis (2 * pi * real_of_int x) = 1" for x
wenzelm@63569
   917
    by (cases x rule: int_diff_cases)
wenzelm@63569
   918
      (simp add: right_diff_distrib cis_divide [symmetric] cis_2pi_nat)
wenzelm@63040
   919
  define c where "c = b - 2 * pi * of_int \<lceil>(b - pi) / (2 * pi)\<rceil>"
huffman@44844
   920
  have "sgn z = cis c"
wenzelm@63569
   921
    by (simp add: b c_def cis_divide [symmetric] cis_2pi_int)
huffman@44844
   922
  moreover have "- pi < c \<and> c \<le> pi"
huffman@44844
   923
    using ceiling_correct [of "(b - pi) / (2*pi)"]
lp15@61649
   924
    by (simp add: c_def less_divide_eq divide_le_eq algebra_simps del: le_of_int_ceiling)
wenzelm@63569
   925
  ultimately show "\<exists>a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi"
wenzelm@63569
   926
    by fast
huffman@44844
   927
qed
huffman@44844
   928
huffman@44844
   929
lemma arg_bounded: "- pi < arg z \<and> arg z \<le> pi"
hoelzl@56889
   930
  by (cases "z = 0") (simp_all add: arg_zero arg_correct)
huffman@44844
   931
huffman@44844
   932
lemma cis_arg: "z \<noteq> 0 \<Longrightarrow> cis (arg z) = sgn z"
huffman@44844
   933
  by (simp add: arg_correct)
huffman@44844
   934
huffman@44844
   935
lemma rcis_cmod_arg: "rcis (cmod z) (arg z) = z"
hoelzl@56889
   936
  by (cases "z = 0") (simp_all add: rcis_def cis_arg sgn_div_norm of_real_def)
hoelzl@56889
   937
hoelzl@56889
   938
lemma cos_arg_i_mult_zero [simp]: "y \<noteq> 0 \<Longrightarrow> Re y = 0 \<Longrightarrow> cos (arg y) = 0"
hoelzl@56889
   939
  using cis_arg [of y] by (simp add: complex_eq_iff)
hoelzl@56889
   940
wenzelm@63569
   941
wenzelm@60758
   942
subsection \<open>Square root of complex numbers\<close>
hoelzl@56889
   943
wenzelm@63569
   944
primcorec csqrt :: "complex \<Rightarrow> complex"
wenzelm@63569
   945
  where
wenzelm@63569
   946
    "Re (csqrt z) = sqrt ((cmod z + Re z) / 2)"
wenzelm@63569
   947
  | "Im (csqrt z) = (if Im z = 0 then 1 else sgn (Im z)) * sqrt ((cmod z - Re z) / 2)"
hoelzl@56889
   948
hoelzl@56889
   949
lemma csqrt_of_real_nonneg [simp]: "Im x = 0 \<Longrightarrow> Re x \<ge> 0 \<Longrightarrow> csqrt x = sqrt (Re x)"
hoelzl@56889
   950
  by (simp add: complex_eq_iff norm_complex_def)
hoelzl@56889
   951
hoelzl@56889
   952
lemma csqrt_of_real_nonpos [simp]: "Im x = 0 \<Longrightarrow> Re x \<le> 0 \<Longrightarrow> csqrt x = \<i> * sqrt \<bar>Re x\<bar>"
hoelzl@56889
   953
  by (simp add: complex_eq_iff norm_complex_def)
hoelzl@56889
   954
lp15@59862
   955
lemma of_real_sqrt: "x \<ge> 0 \<Longrightarrow> of_real (sqrt x) = csqrt (of_real x)"
lp15@59862
   956
  by (simp add: complex_eq_iff norm_complex_def)
lp15@59862
   957
hoelzl@56889
   958
lemma csqrt_0 [simp]: "csqrt 0 = 0"
hoelzl@56889
   959
  by simp
hoelzl@56889
   960
hoelzl@56889
   961
lemma csqrt_1 [simp]: "csqrt 1 = 1"
hoelzl@56889
   962
  by simp
hoelzl@56889
   963
hoelzl@56889
   964
lemma csqrt_ii [simp]: "csqrt \<i> = (1 + \<i>) / sqrt 2"
hoelzl@56889
   965
  by (simp add: complex_eq_iff Re_divide Im_divide real_sqrt_divide real_div_sqrt)
huffman@44844
   966
lp15@59741
   967
lemma power2_csqrt[simp,algebra]: "(csqrt z)\<^sup>2 = z"
wenzelm@63569
   968
proof (cases "Im z = 0")
wenzelm@63569
   969
  case True
wenzelm@63569
   970
  then show ?thesis
hoelzl@56889
   971
    using real_sqrt_pow2[of "Re z"] real_sqrt_pow2[of "- Re z"]
hoelzl@56889
   972
    by (cases "0::real" "Re z" rule: linorder_cases)
wenzelm@63569
   973
      (simp_all add: complex_eq_iff Re_power2 Im_power2 power2_eq_square cmod_eq_Re)
hoelzl@56889
   974
next
wenzelm@63569
   975
  case False
wenzelm@63569
   976
  moreover have "cmod z * cmod z - Re z * Re z = Im z * Im z"
hoelzl@56889
   977
    by (simp add: norm_complex_def power2_eq_square)
wenzelm@63569
   978
  moreover have "\<bar>Re z\<bar> \<le> cmod z"
hoelzl@56889
   979
    by (simp add: norm_complex_def)
hoelzl@56889
   980
  ultimately show ?thesis
hoelzl@56889
   981
    by (simp add: Re_power2 Im_power2 complex_eq_iff real_sgn_eq
wenzelm@63569
   982
        field_simps real_sqrt_mult[symmetric] real_sqrt_divide)
hoelzl@56889
   983
qed
hoelzl@56889
   984
hoelzl@56889
   985
lemma csqrt_eq_0 [simp]: "csqrt z = 0 \<longleftrightarrow> z = 0"
hoelzl@56889
   986
  by auto (metis power2_csqrt power_eq_0_iff)
hoelzl@56889
   987
hoelzl@56889
   988
lemma csqrt_eq_1 [simp]: "csqrt z = 1 \<longleftrightarrow> z = 1"
hoelzl@56889
   989
  by auto (metis power2_csqrt power2_eq_1_iff)
hoelzl@56889
   990
hoelzl@56889
   991
lemma csqrt_principal: "0 < Re (csqrt z) \<or> Re (csqrt z) = 0 \<and> 0 \<le> Im (csqrt z)"
hoelzl@56889
   992
  by (auto simp add: not_less cmod_plus_Re_le_0_iff Im_eq_0)
hoelzl@56889
   993
hoelzl@56889
   994
lemma Re_csqrt: "0 \<le> Re (csqrt z)"
hoelzl@56889
   995
  by (metis csqrt_principal le_less)
hoelzl@56889
   996
hoelzl@56889
   997
lemma csqrt_square:
hoelzl@56889
   998
  assumes "0 < Re b \<or> (Re b = 0 \<and> 0 \<le> Im b)"
hoelzl@56889
   999
  shows "csqrt (b^2) = b"
hoelzl@56889
  1000
proof -
hoelzl@56889
  1001
  have "csqrt (b^2) = b \<or> csqrt (b^2) = - b"
wenzelm@63569
  1002
    by (simp add: power2_eq_iff[symmetric])
hoelzl@56889
  1003
  moreover have "csqrt (b^2) \<noteq> -b \<or> b = 0"
wenzelm@63569
  1004
    using csqrt_principal[of "b ^ 2"] assms
wenzelm@63569
  1005
    by (intro disjCI notI) (auto simp: complex_eq_iff)
hoelzl@56889
  1006
  ultimately show ?thesis
hoelzl@56889
  1007
    by auto
hoelzl@56889
  1008
qed
hoelzl@56889
  1009
wenzelm@63569
  1010
lemma csqrt_unique: "w\<^sup>2 = z \<Longrightarrow> 0 < Re w \<or> Re w = 0 \<and> 0 \<le> Im w \<Longrightarrow> csqrt z = w"
lp15@59746
  1011
  by (auto simp: csqrt_square)
lp15@59746
  1012
lp15@59613
  1013
lemma csqrt_minus [simp]:
hoelzl@56889
  1014
  assumes "Im x < 0 \<or> (Im x = 0 \<and> 0 \<le> Re x)"
hoelzl@56889
  1015
  shows "csqrt (- x) = \<i> * csqrt x"
hoelzl@56889
  1016
proof -
hoelzl@56889
  1017
  have "csqrt ((\<i> * csqrt x)^2) = \<i> * csqrt x"
hoelzl@56889
  1018
  proof (rule csqrt_square)
hoelzl@56889
  1019
    have "Im (csqrt x) \<le> 0"
hoelzl@56889
  1020
      using assms by (auto simp add: cmod_eq_Re mult_le_0_iff field_simps complex_Re_le_cmod)
hoelzl@56889
  1021
    then show "0 < Re (\<i> * csqrt x) \<or> Re (\<i> * csqrt x) = 0 \<and> 0 \<le> Im (\<i> * csqrt x)"
hoelzl@56889
  1022
      by (auto simp add: Re_csqrt simp del: csqrt.simps)
hoelzl@56889
  1023
  qed
hoelzl@56889
  1024
  also have "(\<i> * csqrt x)^2 = - x"
lp15@59746
  1025
    by (simp add: power_mult_distrib)
hoelzl@56889
  1026
  finally show ?thesis .
hoelzl@56889
  1027
qed
huffman@44844
  1028
wenzelm@63569
  1029
wenzelm@60758
  1030
text \<open>Legacy theorem names\<close>
huffman@44065
  1031
huffman@44065
  1032
lemmas expand_complex_eq = complex_eq_iff
huffman@44065
  1033
lemmas complex_Re_Im_cancel_iff = complex_eq_iff
huffman@44065
  1034
lemmas complex_equality = complex_eqI
hoelzl@56889
  1035
lemmas cmod_def = norm_complex_def
hoelzl@56889
  1036
lemmas complex_norm_def = norm_complex_def
hoelzl@56889
  1037
lemmas complex_divide_def = divide_complex_def
hoelzl@56889
  1038
hoelzl@56889
  1039
lemma legacy_Complex_simps:
hoelzl@56889
  1040
  shows Complex_eq_0: "Complex a b = 0 \<longleftrightarrow> a = 0 \<and> b = 0"
hoelzl@56889
  1041
    and complex_add: "Complex a b + Complex c d = Complex (a + c) (b + d)"
hoelzl@56889
  1042
    and complex_minus: "- (Complex a b) = Complex (- a) (- b)"
hoelzl@56889
  1043
    and complex_diff: "Complex a b - Complex c d = Complex (a - c) (b - d)"
hoelzl@56889
  1044
    and Complex_eq_1: "Complex a b = 1 \<longleftrightarrow> a = 1 \<and> b = 0"
hoelzl@56889
  1045
    and Complex_eq_neg_1: "Complex a b = - 1 \<longleftrightarrow> a = - 1 \<and> b = 0"
hoelzl@56889
  1046
    and complex_mult: "Complex a b * Complex c d = Complex (a * c - b * d) (a * d + b * c)"
hoelzl@56889
  1047
    and complex_inverse: "inverse (Complex a b) = Complex (a / (a\<^sup>2 + b\<^sup>2)) (- b / (a\<^sup>2 + b\<^sup>2))"
hoelzl@56889
  1048
    and Complex_eq_numeral: "Complex a b = numeral w \<longleftrightarrow> a = numeral w \<and> b = 0"
hoelzl@56889
  1049
    and Complex_eq_neg_numeral: "Complex a b = - numeral w \<longleftrightarrow> a = - numeral w \<and> b = 0"
hoelzl@56889
  1050
    and complex_scaleR: "scaleR r (Complex a b) = Complex (r * a) (r * b)"
wenzelm@63569
  1051
    and Complex_eq_i: "Complex x y = \<i> \<longleftrightarrow> x = 0 \<and> y = 1"
wenzelm@63569
  1052
    and i_mult_Complex: "\<i> * Complex a b = Complex (- b) a"
wenzelm@63569
  1053
    and Complex_mult_i: "Complex a b * \<i> = Complex (- b) a"
wenzelm@63569
  1054
    and i_complex_of_real: "\<i> * complex_of_real r = Complex 0 r"
wenzelm@63569
  1055
    and complex_of_real_i: "complex_of_real r * \<i> = Complex 0 r"
hoelzl@56889
  1056
    and Complex_add_complex_of_real: "Complex x y + complex_of_real r = Complex (x+r) y"
hoelzl@56889
  1057
    and complex_of_real_add_Complex: "complex_of_real r + Complex x y = Complex (r+x) y"
hoelzl@56889
  1058
    and Complex_mult_complex_of_real: "Complex x y * complex_of_real r = Complex (x*r) (y*r)"
hoelzl@56889
  1059
    and complex_of_real_mult_Complex: "complex_of_real r * Complex x y = Complex (r*x) (r*y)"
wenzelm@63569
  1060
    and complex_eq_cancel_iff2: "(Complex x y = complex_of_real xa) = (x = xa \<and> y = 0)"
hoelzl@56889
  1061
    and complex_cn: "cnj (Complex a b) = Complex a (- b)"
nipkow@64267
  1062
    and Complex_sum': "sum (\<lambda>x. Complex (f x) 0) s = Complex (sum f s) 0"
nipkow@64267
  1063
    and Complex_sum: "Complex (sum f s) 0 = sum (\<lambda>x. Complex (f x) 0) s"
hoelzl@56889
  1064
    and complex_of_real_def: "complex_of_real r = Complex r 0"
hoelzl@56889
  1065
    and complex_norm: "cmod (Complex x y) = sqrt (x\<^sup>2 + y\<^sup>2)"
lp15@65274
  1066
  by (simp_all add: norm_complex_def field_simps complex_eq_iff Re_divide Im_divide)
hoelzl@56889
  1067
hoelzl@56889
  1068
lemma Complex_in_Reals: "Complex x 0 \<in> \<real>"
hoelzl@56889
  1069
  by (metis Reals_of_real complex_of_real_def)
huffman@44065
  1070
paulson@13957
  1071
end