src/HOL/Complex.thy
author paulson <lp15@cam.ac.uk>
Tue Nov 10 14:18:41 2015 +0000 (2015-11-10)
changeset 61609 77b453bd616f
parent 61552 980dd46a03fb
child 61649 268d88ec9087
permissions -rw-r--r--
Coercion "real" now has type nat => real only and is no longer overloaded. Type class "real_of" is gone. Many duplicate theorems removed.
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(*  Title:       HOL/Complex.thy
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    Author:      Jacques D. Fleuriot
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    Copyright:   2001 University of Edinburgh
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    Conversion to Isar and new proofs by 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 @{text codatatype} command to define the type of complex numbers. This allows us to use
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@{text primcorec} to define complex functions by defining their real and imaginary result
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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?]: "\<lbrakk>Re x = Re y; Im x = Im y\<rbrakk> \<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 where
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  "Re 0 = 0"
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| "Im 0 = 0"
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primcorec plus_complex 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 where
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  "Re (- x) = - Re x"
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| "Im (- x) = - Im x"
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primcorec minus_complex 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 intro_classes (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 where
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  "Re 1 = 1"
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| "Im 1 = 0"
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primcorec times_complex 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 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::complex) = x * inverse y"
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instance
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  by intro_classes
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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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  unfolding divide_complex_def by (simp add: 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_all 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 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 Reals\<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: "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: "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]:
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    "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)" by simp
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  also have "Re \<dots> = fact n" 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 "ii" :: complex  ("\<i>") where
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  "Re ii = 0"
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| "Im ii = 1"
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lemma Complex_eq[simp]: "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]: "ii * ii = -1"
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  by (simp add: complex_eq_iff)
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lemma power2_i [simp]: "ii\<^sup>2 = -1"
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  by (simp add: power2_eq_square)
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lemma inverse_i [simp]: "inverse ii = - ii"
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  by (rule inverse_unique) simp
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lemma divide_i [simp]: "x / ii = - ii * x"
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  by (simp add: divide_complex_def)
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lemma complex_i_mult_minus [simp]: "ii * (ii * x) = - x"
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  by (simp add: mult.assoc [symmetric])
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lemma complex_i_not_zero [simp]: "ii \<noteq> 0"
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  by (simp add: complex_eq_iff)
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lemma complex_i_not_one [simp]: "ii \<noteq> 1"
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  by (simp add: complex_eq_iff)
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lemma complex_i_not_numeral [simp]: "ii \<noteq> numeral w"
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  by (simp add: complex_eq_iff)
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lemma complex_i_not_neg_numeral [simp]: "ii \<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_ii_times [simp]: "Re (ii*z) = - Im z"
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  by simp
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lemma Im_ii_times [simp]: "Im (ii*z) = Re z"
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  by simp
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lemma ii_times_eq_iff: "ii*w = z \<longleftrightarrow> w = -(ii*z)"
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  by auto
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lemma divide_numeral_i [simp]: "z / (numeral n * ii) = -(ii*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:
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  "sgn x = x /\<^sub>R cmod x"
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definition dist_complex_def:
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  "dist x y = cmod (x - y)"
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definition open_complex_def:
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  "open (S :: complex set) \<longleftrightarrow> (\<forall>x\<in>S. \<exists>e>0. \<forall>y. dist y x < e \<longrightarrow> y \<in> S)"
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instance 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] 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] power2_eq_square algebra_simps)
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qed (rule complex_sgn_def dist_complex_def open_complex_def)+
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end
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lemma norm_ii [simp]: "norm ii = 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
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  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>"
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  apply (subst complex_eq)
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  apply (rule order_trans)
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  apply (rule norm_triangle_ineq)
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  apply (simp add: norm_mult)
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  done
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lemma cmod_eq_Re: "Im z = 0 \<Longrightarrow> cmod z = \<bar>Re z\<bar>"
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  by (simp add: norm_complex_def)
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lemma cmod_eq_Im: "Re z = 0 \<Longrightarrow> cmod z = \<bar>Im z\<bar>"
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  by (simp add: norm_complex_def)
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   321
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   322
lemma cmod_power2: "cmod z ^ 2 = (Re z)^2 + (Im z)^2"
hoelzl@56889
   323
  by (simp add: norm_complex_def)
hoelzl@56889
   324
hoelzl@56889
   325
lemma cmod_plus_Re_le_0_iff: "cmod z + Re z \<le> 0 \<longleftrightarrow> Re z = - cmod z"
hoelzl@56889
   326
  using abs_Re_le_cmod[of z] by auto
hoelzl@56889
   327
hoelzl@56889
   328
lemma Im_eq_0: "\<bar>Re z\<bar> = cmod z \<Longrightarrow> Im z = 0"
hoelzl@56889
   329
  by (subst (asm) power_eq_iff_eq_base[symmetric, where n=2])
hoelzl@56889
   330
     (auto simp add: norm_complex_def)
hoelzl@56369
   331
hoelzl@56369
   332
lemma abs_sqrt_wlog:
hoelzl@56369
   333
  fixes x::"'a::linordered_idom"
hoelzl@56369
   334
  assumes "\<And>x::'a. x \<ge> 0 \<Longrightarrow> P x (x\<^sup>2)" shows "P \<bar>x\<bar> (x\<^sup>2)"
hoelzl@56369
   335
by (metis abs_ge_zero assms power2_abs)
hoelzl@56369
   336
hoelzl@56369
   337
lemma complex_abs_le_norm: "\<bar>Re z\<bar> + \<bar>Im z\<bar> \<le> sqrt 2 * norm z"
hoelzl@56889
   338
  unfolding norm_complex_def
hoelzl@56369
   339
  apply (rule abs_sqrt_wlog [where x="Re z"])
hoelzl@56369
   340
  apply (rule abs_sqrt_wlog [where x="Im z"])
hoelzl@56369
   341
  apply (rule power2_le_imp_le)
haftmann@57512
   342
  apply (simp_all add: power2_sum add.commute sum_squares_bound real_sqrt_mult [symmetric])
hoelzl@56369
   343
  done
hoelzl@56369
   344
lp15@59741
   345
lemma complex_unit_circle: "z \<noteq> 0 \<Longrightarrow> (Re z / cmod z)\<^sup>2 + (Im z / cmod z)\<^sup>2 = 1"
lp15@59741
   346
  by (simp add: norm_complex_def divide_simps complex_eq_iff)
lp15@59741
   347
hoelzl@56369
   348
wenzelm@60758
   349
text \<open>Properties of complex signum.\<close>
huffman@44843
   350
huffman@44843
   351
lemma sgn_eq: "sgn z = z / complex_of_real (cmod z)"
haftmann@57512
   352
  by (simp add: sgn_div_norm divide_inverse scaleR_conv_of_real mult.commute)
huffman@44843
   353
huffman@44843
   354
lemma Re_sgn [simp]: "Re(sgn z) = Re(z)/cmod z"
huffman@44843
   355
  by (simp add: complex_sgn_def divide_inverse)
huffman@44843
   356
huffman@44843
   357
lemma Im_sgn [simp]: "Im(sgn z) = Im(z)/cmod z"
huffman@44843
   358
  by (simp add: complex_sgn_def divide_inverse)
huffman@44843
   359
paulson@14354
   360
wenzelm@60758
   361
subsection \<open>Completeness of the Complexes\<close>
huffman@23123
   362
huffman@44290
   363
lemma bounded_linear_Re: "bounded_linear Re"
hoelzl@56889
   364
  by (rule bounded_linear_intro [where K=1], simp_all add: norm_complex_def)
huffman@44290
   365
huffman@44290
   366
lemma bounded_linear_Im: "bounded_linear Im"
hoelzl@56889
   367
  by (rule bounded_linear_intro [where K=1], simp_all add: norm_complex_def)
huffman@23123
   368
huffman@44290
   369
lemmas Cauchy_Re = bounded_linear.Cauchy [OF bounded_linear_Re]
huffman@44290
   370
lemmas Cauchy_Im = bounded_linear.Cauchy [OF bounded_linear_Im]
hoelzl@56381
   371
lemmas tendsto_Re [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_Re]
hoelzl@56381
   372
lemmas tendsto_Im [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_Im]
hoelzl@56381
   373
lemmas isCont_Re [simp] = bounded_linear.isCont [OF bounded_linear_Re]
hoelzl@56381
   374
lemmas isCont_Im [simp] = bounded_linear.isCont [OF bounded_linear_Im]
hoelzl@56381
   375
lemmas continuous_Re [simp] = bounded_linear.continuous [OF bounded_linear_Re]
hoelzl@56381
   376
lemmas continuous_Im [simp] = bounded_linear.continuous [OF bounded_linear_Im]
hoelzl@56381
   377
lemmas continuous_on_Re [continuous_intros] = bounded_linear.continuous_on[OF bounded_linear_Re]
hoelzl@56381
   378
lemmas continuous_on_Im [continuous_intros] = bounded_linear.continuous_on[OF bounded_linear_Im]
hoelzl@56381
   379
lemmas has_derivative_Re [derivative_intros] = bounded_linear.has_derivative[OF bounded_linear_Re]
hoelzl@56381
   380
lemmas has_derivative_Im [derivative_intros] = bounded_linear.has_derivative[OF bounded_linear_Im]
hoelzl@56381
   381
lemmas sums_Re = bounded_linear.sums [OF bounded_linear_Re]
hoelzl@56381
   382
lemmas sums_Im = bounded_linear.sums [OF bounded_linear_Im]
hoelzl@56369
   383
huffman@36825
   384
lemma tendsto_Complex [tendsto_intros]:
hoelzl@56889
   385
  "(f ---> a) F \<Longrightarrow> (g ---> b) F \<Longrightarrow> ((\<lambda>x. Complex (f x) (g x)) ---> Complex a b) F"
hoelzl@56889
   386
  by (auto intro!: tendsto_intros)
hoelzl@56369
   387
hoelzl@56369
   388
lemma tendsto_complex_iff:
hoelzl@56369
   389
  "(f ---> x) F \<longleftrightarrow> (((\<lambda>x. Re (f x)) ---> Re x) F \<and> ((\<lambda>x. Im (f x)) ---> Im x) F)"
hoelzl@56889
   390
proof safe
hoelzl@56889
   391
  assume "((\<lambda>x. Re (f x)) ---> Re x) F" "((\<lambda>x. Im (f x)) ---> Im x) F"
hoelzl@56889
   392
  from tendsto_Complex[OF this] show "(f ---> x) F"
hoelzl@56889
   393
    unfolding complex.collapse .
hoelzl@56889
   394
qed (auto intro: tendsto_intros)
hoelzl@56369
   395
hoelzl@57259
   396
lemma continuous_complex_iff: "continuous F f \<longleftrightarrow>
hoelzl@57259
   397
    continuous F (\<lambda>x. Re (f x)) \<and> continuous F (\<lambda>x. Im (f x))"
hoelzl@57259
   398
  unfolding continuous_def tendsto_complex_iff ..
hoelzl@57259
   399
hoelzl@57259
   400
lemma has_vector_derivative_complex_iff: "(f has_vector_derivative x) F \<longleftrightarrow>
hoelzl@57259
   401
    ((\<lambda>x. Re (f x)) has_field_derivative (Re x)) F \<and>
hoelzl@57259
   402
    ((\<lambda>x. Im (f x)) has_field_derivative (Im x)) F"
hoelzl@57259
   403
  unfolding has_vector_derivative_def has_field_derivative_def has_derivative_def tendsto_complex_iff
hoelzl@57259
   404
  by (simp add: field_simps bounded_linear_scaleR_left bounded_linear_mult_right)
hoelzl@57259
   405
hoelzl@57259
   406
lemma has_field_derivative_Re[derivative_intros]:
hoelzl@57259
   407
  "(f has_vector_derivative D) F \<Longrightarrow> ((\<lambda>x. Re (f x)) has_field_derivative (Re D)) F"
hoelzl@57259
   408
  unfolding has_vector_derivative_complex_iff by safe
hoelzl@57259
   409
hoelzl@57259
   410
lemma has_field_derivative_Im[derivative_intros]:
hoelzl@57259
   411
  "(f has_vector_derivative D) F \<Longrightarrow> ((\<lambda>x. Im (f x)) has_field_derivative (Im D)) F"
hoelzl@57259
   412
  unfolding has_vector_derivative_complex_iff by safe
hoelzl@57259
   413
huffman@23123
   414
instance complex :: banach
huffman@23123
   415
proof
huffman@23123
   416
  fix X :: "nat \<Rightarrow> complex"
huffman@23123
   417
  assume X: "Cauchy X"
hoelzl@56889
   418
  then have "(\<lambda>n. Complex (Re (X n)) (Im (X n))) ----> Complex (lim (\<lambda>n. Re (X n))) (lim (\<lambda>n. Im (X n)))"
hoelzl@56889
   419
    by (intro tendsto_Complex convergent_LIMSEQ_iff[THEN iffD1] Cauchy_convergent_iff[THEN iffD1] Cauchy_Re Cauchy_Im)
hoelzl@56889
   420
  then show "convergent X"
hoelzl@56889
   421
    unfolding complex.collapse by (rule convergentI)
huffman@23123
   422
qed
huffman@23123
   423
lp15@56238
   424
declare
hoelzl@56381
   425
  DERIV_power[where 'a=complex, unfolded of_nat_def[symmetric], derivative_intros]
lp15@56238
   426
wenzelm@60758
   427
subsection \<open>Complex Conjugation\<close>
huffman@23125
   428
hoelzl@56889
   429
primcorec cnj :: "complex \<Rightarrow> complex" where
hoelzl@56889
   430
  "Re (cnj z) = Re z"
hoelzl@56889
   431
| "Im (cnj z) = - Im z"
huffman@23125
   432
huffman@23125
   433
lemma complex_cnj_cancel_iff [simp]: "(cnj x = cnj y) = (x = y)"
huffman@44724
   434
  by (simp add: complex_eq_iff)
huffman@23125
   435
huffman@23125
   436
lemma complex_cnj_cnj [simp]: "cnj (cnj z) = z"
hoelzl@56889
   437
  by (simp add: complex_eq_iff)
huffman@23125
   438
huffman@23125
   439
lemma complex_cnj_zero [simp]: "cnj 0 = 0"
huffman@44724
   440
  by (simp add: complex_eq_iff)
huffman@23125
   441
huffman@23125
   442
lemma complex_cnj_zero_iff [iff]: "(cnj z = 0) = (z = 0)"
huffman@44724
   443
  by (simp add: complex_eq_iff)
huffman@23125
   444
hoelzl@56889
   445
lemma complex_cnj_add [simp]: "cnj (x + y) = cnj x + cnj y"
huffman@44724
   446
  by (simp add: complex_eq_iff)
huffman@23125
   447
hoelzl@56889
   448
lemma cnj_setsum [simp]: "cnj (setsum f s) = (\<Sum>x\<in>s. cnj (f x))"
hoelzl@56889
   449
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   450
hoelzl@56889
   451
lemma complex_cnj_diff [simp]: "cnj (x - y) = cnj x - cnj y"
huffman@44724
   452
  by (simp add: complex_eq_iff)
huffman@23125
   453
hoelzl@56889
   454
lemma complex_cnj_minus [simp]: "cnj (- x) = - cnj x"
huffman@44724
   455
  by (simp add: complex_eq_iff)
huffman@23125
   456
huffman@23125
   457
lemma complex_cnj_one [simp]: "cnj 1 = 1"
huffman@44724
   458
  by (simp add: complex_eq_iff)
huffman@23125
   459
hoelzl@56889
   460
lemma complex_cnj_mult [simp]: "cnj (x * y) = cnj x * cnj y"
huffman@44724
   461
  by (simp add: complex_eq_iff)
huffman@23125
   462
hoelzl@56889
   463
lemma cnj_setprod [simp]: "cnj (setprod f s) = (\<Prod>x\<in>s. cnj (f x))"
hoelzl@56889
   464
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   465
hoelzl@56889
   466
lemma complex_cnj_inverse [simp]: "cnj (inverse x) = inverse (cnj x)"
hoelzl@56889
   467
  by (simp add: complex_eq_iff)
paulson@14323
   468
hoelzl@56889
   469
lemma complex_cnj_divide [simp]: "cnj (x / y) = cnj x / cnj y"
hoelzl@56889
   470
  by (simp add: divide_complex_def)
huffman@23125
   471
hoelzl@56889
   472
lemma complex_cnj_power [simp]: "cnj (x ^ n) = cnj x ^ n"
hoelzl@56889
   473
  by (induct n) simp_all
huffman@23125
   474
huffman@23125
   475
lemma complex_cnj_of_nat [simp]: "cnj (of_nat n) = of_nat n"
huffman@44724
   476
  by (simp add: complex_eq_iff)
huffman@23125
   477
huffman@23125
   478
lemma complex_cnj_of_int [simp]: "cnj (of_int z) = of_int z"
huffman@44724
   479
  by (simp add: complex_eq_iff)
huffman@23125
   480
huffman@47108
   481
lemma complex_cnj_numeral [simp]: "cnj (numeral w) = numeral w"
huffman@47108
   482
  by (simp add: complex_eq_iff)
huffman@47108
   483
haftmann@54489
   484
lemma complex_cnj_neg_numeral [simp]: "cnj (- numeral w) = - numeral w"
huffman@44724
   485
  by (simp add: complex_eq_iff)
huffman@23125
   486
hoelzl@56889
   487
lemma complex_cnj_scaleR [simp]: "cnj (scaleR r x) = scaleR r (cnj x)"
huffman@44724
   488
  by (simp add: complex_eq_iff)
huffman@23125
   489
huffman@23125
   490
lemma complex_mod_cnj [simp]: "cmod (cnj z) = cmod z"
hoelzl@56889
   491
  by (simp add: norm_complex_def)
paulson@14323
   492
huffman@23125
   493
lemma complex_cnj_complex_of_real [simp]: "cnj (of_real x) = of_real x"
huffman@44724
   494
  by (simp add: complex_eq_iff)
huffman@23125
   495
huffman@23125
   496
lemma complex_cnj_i [simp]: "cnj ii = - ii"
huffman@44724
   497
  by (simp add: complex_eq_iff)
huffman@23125
   498
huffman@23125
   499
lemma complex_add_cnj: "z + cnj z = complex_of_real (2 * Re z)"
huffman@44724
   500
  by (simp add: complex_eq_iff)
huffman@23125
   501
huffman@23125
   502
lemma complex_diff_cnj: "z - cnj z = complex_of_real (2 * Im z) * ii"
huffman@44724
   503
  by (simp add: complex_eq_iff)
paulson@14354
   504
wenzelm@53015
   505
lemma complex_mult_cnj: "z * cnj z = complex_of_real ((Re z)\<^sup>2 + (Im z)\<^sup>2)"
huffman@44724
   506
  by (simp add: complex_eq_iff power2_eq_square)
huffman@23125
   507
wenzelm@53015
   508
lemma complex_mod_mult_cnj: "cmod (z * cnj z) = (cmod z)\<^sup>2"
huffman@44724
   509
  by (simp add: norm_mult power2_eq_square)
huffman@23125
   510
huffman@44827
   511
lemma complex_mod_sqrt_Re_mult_cnj: "cmod z = sqrt (Re (z * cnj z))"
hoelzl@56889
   512
  by (simp add: norm_complex_def power2_eq_square)
huffman@44827
   513
huffman@44827
   514
lemma complex_In_mult_cnj_zero [simp]: "Im (z * cnj z) = 0"
huffman@44827
   515
  by simp
huffman@44827
   516
eberlm@61531
   517
lemma complex_cnj_fact [simp]: "cnj (fact n) = fact n"
eberlm@61531
   518
  by (subst of_nat_fact [symmetric], subst complex_cnj_of_nat) simp
eberlm@61531
   519
eberlm@61531
   520
lemma complex_cnj_pochhammer [simp]: "cnj (pochhammer z n) = pochhammer (cnj z) n"
eberlm@61531
   521
  by (induction n arbitrary: z) (simp_all add: pochhammer_rec)
eberlm@61531
   522
huffman@44290
   523
lemma bounded_linear_cnj: "bounded_linear cnj"
huffman@44127
   524
  using complex_cnj_add complex_cnj_scaleR
huffman@44127
   525
  by (rule bounded_linear_intro [where K=1], simp)
paulson@14354
   526
hoelzl@56381
   527
lemmas tendsto_cnj [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_cnj]
hoelzl@56381
   528
lemmas isCont_cnj [simp] = bounded_linear.isCont [OF bounded_linear_cnj]
hoelzl@56381
   529
lemmas continuous_cnj [simp, continuous_intros] = bounded_linear.continuous [OF bounded_linear_cnj]
hoelzl@56381
   530
lemmas continuous_on_cnj [simp, continuous_intros] = bounded_linear.continuous_on [OF bounded_linear_cnj]
hoelzl@56381
   531
lemmas has_derivative_cnj [simp, derivative_intros] = bounded_linear.has_derivative [OF bounded_linear_cnj]
huffman@44290
   532
hoelzl@56369
   533
lemma lim_cnj: "((\<lambda>x. cnj(f x)) ---> cnj l) F \<longleftrightarrow> (f ---> l) F"
hoelzl@56889
   534
  by (simp add: tendsto_iff dist_complex_def complex_cnj_diff [symmetric] del: complex_cnj_diff)
hoelzl@56369
   535
hoelzl@56369
   536
lemma sums_cnj: "((\<lambda>x. cnj(f x)) sums cnj l) \<longleftrightarrow> (f sums l)"
hoelzl@56889
   537
  by (simp add: sums_def lim_cnj cnj_setsum [symmetric] del: cnj_setsum)
hoelzl@56369
   538
paulson@14354
   539
wenzelm@60758
   540
subsection\<open>Basic Lemmas\<close>
lp15@55734
   541
lp15@55734
   542
lemma complex_eq_0: "z=0 \<longleftrightarrow> (Re z)\<^sup>2 + (Im z)\<^sup>2 = 0"
hoelzl@56889
   543
  by (metis zero_complex.sel complex_eqI sum_power2_eq_zero_iff)
lp15@55734
   544
lp15@55734
   545
lemma complex_neq_0: "z\<noteq>0 \<longleftrightarrow> (Re z)\<^sup>2 + (Im z)\<^sup>2 > 0"
hoelzl@56889
   546
  by (metis complex_eq_0 less_numeral_extra(3) sum_power2_gt_zero_iff)
lp15@55734
   547
lp15@55734
   548
lemma complex_norm_square: "of_real ((norm z)\<^sup>2) = z * cnj z"
hoelzl@56889
   549
by (cases z)
hoelzl@56889
   550
   (auto simp: complex_eq_iff norm_complex_def power2_eq_square[symmetric] of_real_power[symmetric]
hoelzl@56889
   551
         simp del: of_real_power)
lp15@55734
   552
paulson@61104
   553
lemma complex_div_cnj: "a / b = (a * cnj b) / (norm b)^2"
paulson@61104
   554
  using complex_norm_square by auto
paulson@61104
   555
lp15@59741
   556
lemma Re_complex_div_eq_0: "Re (a / b) = 0 \<longleftrightarrow> Re (a * cnj b) = 0"
hoelzl@56889
   557
  by (auto simp add: Re_divide)
lp15@59613
   558
lp15@59741
   559
lemma Im_complex_div_eq_0: "Im (a / b) = 0 \<longleftrightarrow> Im (a * cnj b) = 0"
hoelzl@56889
   560
  by (auto simp add: Im_divide)
hoelzl@56889
   561
lp15@59613
   562
lemma complex_div_gt_0:
hoelzl@56889
   563
  "(Re (a / b) > 0 \<longleftrightarrow> Re (a * cnj b) > 0) \<and> (Im (a / b) > 0 \<longleftrightarrow> Im (a * cnj b) > 0)"
hoelzl@56889
   564
proof cases
hoelzl@56889
   565
  assume "b = 0" then show ?thesis by auto
lp15@55734
   566
next
hoelzl@56889
   567
  assume "b \<noteq> 0"
hoelzl@56889
   568
  then have "0 < (Re b)\<^sup>2 + (Im b)\<^sup>2"
hoelzl@56889
   569
    by (simp add: complex_eq_iff sum_power2_gt_zero_iff)
hoelzl@56889
   570
  then show ?thesis
hoelzl@56889
   571
    by (simp add: Re_divide Im_divide zero_less_divide_iff)
lp15@55734
   572
qed
lp15@55734
   573
lp15@59741
   574
lemma Re_complex_div_gt_0: "Re (a / b) > 0 \<longleftrightarrow> Re (a * cnj b) > 0"
lp15@59741
   575
  and Im_complex_div_gt_0: "Im (a / b) > 0 \<longleftrightarrow> Im (a * cnj b) > 0"
hoelzl@56889
   576
  using complex_div_gt_0 by auto
lp15@55734
   577
lp15@59741
   578
lemma Re_complex_div_ge_0: "Re(a / b) \<ge> 0 \<longleftrightarrow> Re(a * cnj b) \<ge> 0"
lp15@59741
   579
  by (metis le_less Re_complex_div_eq_0 Re_complex_div_gt_0)
lp15@55734
   580
lp15@59741
   581
lemma Im_complex_div_ge_0: "Im(a / b) \<ge> 0 \<longleftrightarrow> Im(a * cnj b) \<ge> 0"
lp15@59741
   582
  by (metis Im_complex_div_eq_0 Im_complex_div_gt_0 le_less)
lp15@55734
   583
lp15@59741
   584
lemma Re_complex_div_lt_0: "Re(a / b) < 0 \<longleftrightarrow> Re(a * cnj b) < 0"
lp15@59741
   585
  by (metis less_asym neq_iff Re_complex_div_eq_0 Re_complex_div_gt_0)
lp15@55734
   586
lp15@59741
   587
lemma Im_complex_div_lt_0: "Im(a / b) < 0 \<longleftrightarrow> Im(a * cnj b) < 0"
lp15@59741
   588
  by (metis Im_complex_div_eq_0 Im_complex_div_gt_0 less_asym neq_iff)
lp15@55734
   589
lp15@59741
   590
lemma Re_complex_div_le_0: "Re(a / b) \<le> 0 \<longleftrightarrow> Re(a * cnj b) \<le> 0"
lp15@59741
   591
  by (metis not_le Re_complex_div_gt_0)
lp15@55734
   592
lp15@59741
   593
lemma Im_complex_div_le_0: "Im(a / b) \<le> 0 \<longleftrightarrow> Im(a * cnj b) \<le> 0"
lp15@59741
   594
  by (metis Im_complex_div_gt_0 not_le)
lp15@55734
   595
paulson@61104
   596
lemma Re_divide_of_real [simp]: "Re (z / of_real r) = Re z / r"
paulson@61104
   597
  by (simp add: Re_divide power2_eq_square)
paulson@61104
   598
paulson@61104
   599
lemma Im_divide_of_real [simp]: "Im (z / of_real r) = Im z / r"
paulson@61104
   600
  by (simp add: Im_divide power2_eq_square)
paulson@61104
   601
paulson@61104
   602
lemma Re_divide_Reals: "r \<in> Reals \<Longrightarrow> Re (z / r) = Re z / Re r"
paulson@61104
   603
  by (metis Re_divide_of_real of_real_Re)
paulson@61104
   604
paulson@61104
   605
lemma Im_divide_Reals: "r \<in> Reals \<Longrightarrow> Im (z / r) = Im z / Re r"
paulson@61104
   606
  by (metis Im_divide_of_real of_real_Re)
paulson@61104
   607
hoelzl@56889
   608
lemma Re_setsum[simp]: "Re (setsum f s) = (\<Sum>x\<in>s. Re (f x))"
hoelzl@56369
   609
  by (induct s rule: infinite_finite_induct) auto
lp15@55734
   610
hoelzl@56889
   611
lemma Im_setsum[simp]: "Im (setsum f s) = (\<Sum>x\<in>s. Im(f x))"
hoelzl@56369
   612
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   613
hoelzl@56369
   614
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)"
hoelzl@56369
   615
  unfolding sums_def tendsto_complex_iff Im_setsum Re_setsum ..
lp15@59613
   616
hoelzl@56369
   617
lemma summable_complex_iff: "summable f \<longleftrightarrow> summable (\<lambda>x. Re (f x)) \<and>  summable (\<lambda>x. Im (f x))"
hoelzl@56889
   618
  unfolding summable_def sums_complex_iff[abs_def] by (metis complex.sel)
hoelzl@56369
   619
hoelzl@56369
   620
lemma summable_complex_of_real [simp]: "summable (\<lambda>n. complex_of_real (f n)) \<longleftrightarrow> summable f"
hoelzl@56369
   621
  unfolding summable_complex_iff by simp
hoelzl@56369
   622
hoelzl@56369
   623
lemma summable_Re: "summable f \<Longrightarrow> summable (\<lambda>x. Re (f x))"
hoelzl@56369
   624
  unfolding summable_complex_iff by blast
hoelzl@56369
   625
hoelzl@56369
   626
lemma summable_Im: "summable f \<Longrightarrow> summable (\<lambda>x. Im (f x))"
hoelzl@56369
   627
  unfolding summable_complex_iff by blast
lp15@56217
   628
paulson@61104
   629
lemma complex_is_Nat_iff: "z \<in> \<nat> \<longleftrightarrow> Im z = 0 \<and> (\<exists>i. Re z = of_nat i)"
paulson@61104
   630
  by (auto simp: Nats_def complex_eq_iff)
paulson@61104
   631
paulson@61104
   632
lemma complex_is_Int_iff: "z \<in> \<int> \<longleftrightarrow> Im z = 0 \<and> (\<exists>i. Re z = of_int i)"
paulson@61104
   633
  by (auto simp: Ints_def complex_eq_iff)
paulson@61104
   634
hoelzl@56889
   635
lemma complex_is_Real_iff: "z \<in> \<real> \<longleftrightarrow> Im z = 0"
hoelzl@56889
   636
  by (auto simp: Reals_def complex_eq_iff)
lp15@55734
   637
lp15@55734
   638
lemma Reals_cnj_iff: "z \<in> \<real> \<longleftrightarrow> cnj z = z"
hoelzl@56889
   639
  by (auto simp: complex_is_Real_iff complex_eq_iff)
lp15@55734
   640
lp15@55734
   641
lemma in_Reals_norm: "z \<in> \<real> \<Longrightarrow> norm(z) = abs(Re z)"
hoelzl@56889
   642
  by (simp add: complex_is_Real_iff norm_complex_def)
hoelzl@56369
   643
hoelzl@56369
   644
lemma series_comparison_complex:
hoelzl@56369
   645
  fixes f:: "nat \<Rightarrow> 'a::banach"
hoelzl@56369
   646
  assumes sg: "summable g"
hoelzl@56369
   647
     and "\<And>n. g n \<in> \<real>" "\<And>n. Re (g n) \<ge> 0"
hoelzl@56369
   648
     and fg: "\<And>n. n \<ge> N \<Longrightarrow> norm(f n) \<le> norm(g n)"
hoelzl@56369
   649
  shows "summable f"
hoelzl@56369
   650
proof -
hoelzl@56369
   651
  have g: "\<And>n. cmod (g n) = Re (g n)" using assms
hoelzl@56369
   652
    by (metis abs_of_nonneg in_Reals_norm)
hoelzl@56369
   653
  show ?thesis
hoelzl@56369
   654
    apply (rule summable_comparison_test' [where g = "\<lambda>n. norm (g n)" and N=N])
hoelzl@56369
   655
    using sg
hoelzl@56369
   656
    apply (auto simp: summable_def)
hoelzl@56369
   657
    apply (rule_tac x="Re s" in exI)
hoelzl@56369
   658
    apply (auto simp: g sums_Re)
hoelzl@56369
   659
    apply (metis fg g)
hoelzl@56369
   660
    done
hoelzl@56369
   661
qed
lp15@55734
   662
wenzelm@60758
   663
subsection\<open>Polar Form for Complex Numbers\<close>
lp15@59746
   664
lp15@59746
   665
lemma complex_unimodular_polar: "(norm z = 1) \<Longrightarrow> \<exists>x. z = Complex (cos x) (sin x)"
lp15@59746
   666
  using sincos_total_2pi [of "Re z" "Im z"]
lp15@59746
   667
  by auto (metis cmod_power2 complex_eq power_one)
paulson@14323
   668
wenzelm@60758
   669
subsubsection \<open>$\cos \theta + i \sin \theta$\<close>
huffman@20557
   670
hoelzl@56889
   671
primcorec cis :: "real \<Rightarrow> complex" where
hoelzl@56889
   672
  "Re (cis a) = cos a"
hoelzl@56889
   673
| "Im (cis a) = sin a"
huffman@44827
   674
huffman@44827
   675
lemma cis_zero [simp]: "cis 0 = 1"
hoelzl@56889
   676
  by (simp add: complex_eq_iff)
huffman@44827
   677
huffman@44828
   678
lemma norm_cis [simp]: "norm (cis a) = 1"
hoelzl@56889
   679
  by (simp add: norm_complex_def)
huffman@44828
   680
huffman@44828
   681
lemma sgn_cis [simp]: "sgn (cis a) = cis a"
huffman@44828
   682
  by (simp add: sgn_div_norm)
huffman@44828
   683
huffman@44828
   684
lemma cis_neq_zero [simp]: "cis a \<noteq> 0"
huffman@44828
   685
  by (metis norm_cis norm_zero zero_neq_one)
huffman@44828
   686
huffman@44827
   687
lemma cis_mult: "cis a * cis b = cis (a + b)"
hoelzl@56889
   688
  by (simp add: complex_eq_iff cos_add sin_add)
huffman@44827
   689
huffman@44827
   690
lemma DeMoivre: "(cis a) ^ n = cis (real n * a)"
lp15@61609
   691
  by (induct n, simp_all add: of_nat_Suc algebra_simps cis_mult)
huffman@44827
   692
huffman@44827
   693
lemma cis_inverse [simp]: "inverse(cis a) = cis (-a)"
hoelzl@56889
   694
  by (simp add: complex_eq_iff)
huffman@44827
   695
huffman@44827
   696
lemma cis_divide: "cis a / cis b = cis (a - b)"
hoelzl@56889
   697
  by (simp add: divide_complex_def cis_mult)
huffman@44827
   698
huffman@44827
   699
lemma cos_n_Re_cis_pow_n: "cos (real n * a) = Re(cis a ^ n)"
huffman@44827
   700
  by (auto simp add: DeMoivre)
huffman@44827
   701
huffman@44827
   702
lemma sin_n_Im_cis_pow_n: "sin (real n * a) = Im(cis a ^ n)"
huffman@44827
   703
  by (auto simp add: DeMoivre)
huffman@44827
   704
hoelzl@56889
   705
lemma cis_pi: "cis pi = -1"
hoelzl@56889
   706
  by (simp add: complex_eq_iff)
hoelzl@56889
   707
wenzelm@60758
   708
subsubsection \<open>$r(\cos \theta + i \sin \theta)$\<close>
huffman@44715
   709
hoelzl@56889
   710
definition rcis :: "real \<Rightarrow> real \<Rightarrow> complex" where
huffman@20557
   711
  "rcis r a = complex_of_real r * cis a"
huffman@20557
   712
huffman@44827
   713
lemma Re_rcis [simp]: "Re(rcis r a) = r * cos a"
huffman@44828
   714
  by (simp add: rcis_def)
huffman@44827
   715
huffman@44827
   716
lemma Im_rcis [simp]: "Im(rcis r a) = r * sin a"
huffman@44828
   717
  by (simp add: rcis_def)
huffman@44827
   718
huffman@44827
   719
lemma rcis_Ex: "\<exists>r a. z = rcis r a"
huffman@44828
   720
  by (simp add: complex_eq_iff polar_Ex)
huffman@44827
   721
huffman@44827
   722
lemma complex_mod_rcis [simp]: "cmod(rcis r a) = abs r"
huffman@44828
   723
  by (simp add: rcis_def norm_mult)
huffman@44827
   724
huffman@44827
   725
lemma cis_rcis_eq: "cis a = rcis 1 a"
huffman@44827
   726
  by (simp add: rcis_def)
huffman@44827
   727
huffman@44827
   728
lemma rcis_mult: "rcis r1 a * rcis r2 b = rcis (r1*r2) (a + b)"
huffman@44828
   729
  by (simp add: rcis_def cis_mult)
huffman@44827
   730
huffman@44827
   731
lemma rcis_zero_mod [simp]: "rcis 0 a = 0"
huffman@44827
   732
  by (simp add: rcis_def)
huffman@44827
   733
huffman@44827
   734
lemma rcis_zero_arg [simp]: "rcis r 0 = complex_of_real r"
huffman@44827
   735
  by (simp add: rcis_def)
huffman@44827
   736
huffman@44828
   737
lemma rcis_eq_zero_iff [simp]: "rcis r a = 0 \<longleftrightarrow> r = 0"
huffman@44828
   738
  by (simp add: rcis_def)
huffman@44828
   739
huffman@44827
   740
lemma DeMoivre2: "(rcis r a) ^ n = rcis (r ^ n) (real n * a)"
huffman@44827
   741
  by (simp add: rcis_def power_mult_distrib DeMoivre)
huffman@44827
   742
huffman@44827
   743
lemma rcis_inverse: "inverse(rcis r a) = rcis (1/r) (-a)"
huffman@44827
   744
  by (simp add: divide_inverse rcis_def)
huffman@44827
   745
huffman@44827
   746
lemma rcis_divide: "rcis r1 a / rcis r2 b = rcis (r1/r2) (a - b)"
huffman@44828
   747
  by (simp add: rcis_def cis_divide [symmetric])
huffman@44827
   748
wenzelm@60758
   749
subsubsection \<open>Complex exponential\<close>
huffman@44827
   750
lp15@59658
   751
abbreviation Exp :: "complex \<Rightarrow> complex"
lp15@59658
   752
  where "Exp \<equiv> exp"
huffman@44291
   753
hoelzl@56889
   754
lemma cis_conv_exp: "cis b = exp (\<i> * b)"
hoelzl@56889
   755
proof -
hoelzl@56889
   756
  { fix n :: nat
hoelzl@56889
   757
    have "\<i> ^ n = fact n *\<^sub>R (cos_coeff n + \<i> * sin_coeff n)"
hoelzl@56889
   758
      by (induct n)
hoelzl@56889
   759
         (simp_all add: sin_coeff_Suc cos_coeff_Suc complex_eq_iff Re_divide Im_divide field_simps
lp15@61609
   760
                        power2_eq_square of_nat_Suc add_nonneg_eq_0_iff)
hoelzl@56889
   761
    then have "(\<i> * complex_of_real b) ^ n /\<^sub>R fact n =
hoelzl@56889
   762
        of_real (cos_coeff n * b^n) + \<i> * of_real (sin_coeff n * b^n)"
hoelzl@56889
   763
      by (simp add: field_simps) }
lp15@59658
   764
  then show ?thesis using sin_converges [of b] cos_converges [of b]
hoelzl@56889
   765
    by (auto simp add: cis.ctr exp_def simp del: of_real_mult
lp15@59658
   766
             intro!: sums_unique sums_add sums_mult sums_of_real)
huffman@44291
   767
qed
huffman@44291
   768
lp15@59658
   769
lemma Exp_eq_polar: "Exp z = exp (Re z) * cis (Im z)"
hoelzl@56889
   770
  unfolding cis_conv_exp exp_of_real [symmetric] mult_exp_exp by (cases z) simp
huffman@20557
   771
huffman@44828
   772
lemma Re_exp: "Re (exp z) = exp (Re z) * cos (Im z)"
lp15@59658
   773
  unfolding Exp_eq_polar by simp
huffman@44828
   774
huffman@44828
   775
lemma Im_exp: "Im (exp z) = exp (Re z) * sin (Im z)"
lp15@59658
   776
  unfolding Exp_eq_polar by simp
huffman@44828
   777
lp15@59746
   778
lemma norm_cos_sin [simp]: "norm (Complex (cos t) (sin t)) = 1"
lp15@59746
   779
  by (simp add: norm_complex_def)
lp15@59746
   780
lp15@59746
   781
lemma norm_exp_eq_Re [simp]: "norm (exp z) = exp (Re z)"
lp15@59746
   782
  by (simp add: cis.code cmod_complex_polar Exp_eq_polar)
lp15@59746
   783
lp15@59658
   784
lemma complex_Exp_Ex: "\<exists>a r. z = complex_of_real r * Exp a"
lp15@59746
   785
  apply (insert rcis_Ex [of z])
lp15@59746
   786
  apply (auto simp add: Exp_eq_polar rcis_def mult.assoc [symmetric])
lp15@59746
   787
  apply (rule_tac x = "ii * complex_of_real a" in exI, auto)
lp15@59746
   788
  done
paulson@14323
   789
lp15@59658
   790
lemma Exp_two_pi_i [simp]: "Exp((2::complex) * complex_of_real pi * ii) = 1"
lp15@59658
   791
  by (simp add: Exp_eq_polar complex_eq_iff)
paulson@14387
   792
wenzelm@60758
   793
subsubsection \<open>Complex argument\<close>
huffman@44844
   794
huffman@44844
   795
definition arg :: "complex \<Rightarrow> real" where
huffman@44844
   796
  "arg z = (if z = 0 then 0 else (SOME a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi))"
huffman@44844
   797
huffman@44844
   798
lemma arg_zero: "arg 0 = 0"
huffman@44844
   799
  by (simp add: arg_def)
huffman@44844
   800
huffman@44844
   801
lemma arg_unique:
huffman@44844
   802
  assumes "sgn z = cis x" and "-pi < x" and "x \<le> pi"
huffman@44844
   803
  shows "arg z = x"
huffman@44844
   804
proof -
huffman@44844
   805
  from assms have "z \<noteq> 0" by auto
huffman@44844
   806
  have "(SOME a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi) = x"
huffman@44844
   807
  proof
huffman@44844
   808
    fix a def d \<equiv> "a - x"
huffman@44844
   809
    assume a: "sgn z = cis a \<and> - pi < a \<and> a \<le> pi"
huffman@44844
   810
    from a assms have "- (2*pi) < d \<and> d < 2*pi"
huffman@44844
   811
      unfolding d_def by simp
huffman@44844
   812
    moreover from a assms have "cos a = cos x" and "sin a = sin x"
huffman@44844
   813
      by (simp_all add: complex_eq_iff)
wenzelm@53374
   814
    hence cos: "cos d = 1" unfolding d_def cos_diff by simp
wenzelm@53374
   815
    moreover from cos have "sin d = 0" by (rule cos_one_sin_zero)
huffman@44844
   816
    ultimately have "d = 0"
haftmann@58709
   817
      unfolding sin_zero_iff
haftmann@58740
   818
      by (auto elim!: evenE dest!: less_2_cases)
huffman@44844
   819
    thus "a = x" unfolding d_def by simp
huffman@44844
   820
  qed (simp add: assms del: Re_sgn Im_sgn)
wenzelm@60758
   821
  with \<open>z \<noteq> 0\<close> show "arg z = x"
huffman@44844
   822
    unfolding arg_def by simp
huffman@44844
   823
qed
huffman@44844
   824
huffman@44844
   825
lemma arg_correct:
huffman@44844
   826
  assumes "z \<noteq> 0" shows "sgn z = cis (arg z) \<and> -pi < arg z \<and> arg z \<le> pi"
huffman@44844
   827
proof (simp add: arg_def assms, rule someI_ex)
huffman@44844
   828
  obtain r a where z: "z = rcis r a" using rcis_Ex by fast
huffman@44844
   829
  with assms have "r \<noteq> 0" by auto
huffman@44844
   830
  def b \<equiv> "if 0 < r then a else a + pi"
huffman@44844
   831
  have b: "sgn z = cis b"
wenzelm@60758
   832
    unfolding z b_def rcis_def using \<open>r \<noteq> 0\<close>
hoelzl@56889
   833
    by (simp add: of_real_def sgn_scaleR sgn_if complex_eq_iff)
huffman@44844
   834
  have cis_2pi_nat: "\<And>n. cis (2 * pi * real_of_nat n) = 1"
hoelzl@56889
   835
    by (induct_tac n) (simp_all add: distrib_left cis_mult [symmetric] complex_eq_iff)
huffman@44844
   836
  have cis_2pi_int: "\<And>x. cis (2 * pi * real_of_int x) = 1"
hoelzl@56889
   837
    by (case_tac x rule: int_diff_cases)
hoelzl@56889
   838
       (simp add: right_diff_distrib cis_divide [symmetric] cis_2pi_nat)
huffman@44844
   839
  def c \<equiv> "b - 2*pi * of_int \<lceil>(b - pi) / (2*pi)\<rceil>"
huffman@44844
   840
  have "sgn z = cis c"
huffman@44844
   841
    unfolding b c_def
huffman@44844
   842
    by (simp add: cis_divide [symmetric] cis_2pi_int)
huffman@44844
   843
  moreover have "- pi < c \<and> c \<le> pi"
huffman@44844
   844
    using ceiling_correct [of "(b - pi) / (2*pi)"]
huffman@44844
   845
    by (simp add: c_def less_divide_eq divide_le_eq algebra_simps)
huffman@44844
   846
  ultimately show "\<exists>a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi" by fast
huffman@44844
   847
qed
huffman@44844
   848
huffman@44844
   849
lemma arg_bounded: "- pi < arg z \<and> arg z \<le> pi"
hoelzl@56889
   850
  by (cases "z = 0") (simp_all add: arg_zero arg_correct)
huffman@44844
   851
huffman@44844
   852
lemma cis_arg: "z \<noteq> 0 \<Longrightarrow> cis (arg z) = sgn z"
huffman@44844
   853
  by (simp add: arg_correct)
huffman@44844
   854
huffman@44844
   855
lemma rcis_cmod_arg: "rcis (cmod z) (arg z) = z"
hoelzl@56889
   856
  by (cases "z = 0") (simp_all add: rcis_def cis_arg sgn_div_norm of_real_def)
hoelzl@56889
   857
hoelzl@56889
   858
lemma cos_arg_i_mult_zero [simp]: "y \<noteq> 0 \<Longrightarrow> Re y = 0 \<Longrightarrow> cos (arg y) = 0"
hoelzl@56889
   859
  using cis_arg [of y] by (simp add: complex_eq_iff)
hoelzl@56889
   860
wenzelm@60758
   861
subsection \<open>Square root of complex numbers\<close>
hoelzl@56889
   862
hoelzl@56889
   863
primcorec csqrt :: "complex \<Rightarrow> complex" where
hoelzl@56889
   864
  "Re (csqrt z) = sqrt ((cmod z + Re z) / 2)"
hoelzl@56889
   865
| "Im (csqrt z) = (if Im z = 0 then 1 else sgn (Im z)) * sqrt ((cmod z - Re z) / 2)"
hoelzl@56889
   866
hoelzl@56889
   867
lemma csqrt_of_real_nonneg [simp]: "Im x = 0 \<Longrightarrow> Re x \<ge> 0 \<Longrightarrow> csqrt x = sqrt (Re x)"
hoelzl@56889
   868
  by (simp add: complex_eq_iff norm_complex_def)
hoelzl@56889
   869
hoelzl@56889
   870
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
   871
  by (simp add: complex_eq_iff norm_complex_def)
hoelzl@56889
   872
lp15@59862
   873
lemma of_real_sqrt: "x \<ge> 0 \<Longrightarrow> of_real (sqrt x) = csqrt (of_real x)"
lp15@59862
   874
  by (simp add: complex_eq_iff norm_complex_def)
lp15@59862
   875
hoelzl@56889
   876
lemma csqrt_0 [simp]: "csqrt 0 = 0"
hoelzl@56889
   877
  by simp
hoelzl@56889
   878
hoelzl@56889
   879
lemma csqrt_1 [simp]: "csqrt 1 = 1"
hoelzl@56889
   880
  by simp
hoelzl@56889
   881
hoelzl@56889
   882
lemma csqrt_ii [simp]: "csqrt \<i> = (1 + \<i>) / sqrt 2"
hoelzl@56889
   883
  by (simp add: complex_eq_iff Re_divide Im_divide real_sqrt_divide real_div_sqrt)
huffman@44844
   884
lp15@59741
   885
lemma power2_csqrt[simp,algebra]: "(csqrt z)\<^sup>2 = z"
hoelzl@56889
   886
proof cases
hoelzl@56889
   887
  assume "Im z = 0" then show ?thesis
hoelzl@56889
   888
    using real_sqrt_pow2[of "Re z"] real_sqrt_pow2[of "- Re z"]
hoelzl@56889
   889
    by (cases "0::real" "Re z" rule: linorder_cases)
hoelzl@56889
   890
       (simp_all add: complex_eq_iff Re_power2 Im_power2 power2_eq_square cmod_eq_Re)
hoelzl@56889
   891
next
hoelzl@56889
   892
  assume "Im z \<noteq> 0"
hoelzl@56889
   893
  moreover
hoelzl@56889
   894
  have "cmod z * cmod z - Re z * Re z = Im z * Im z"
hoelzl@56889
   895
    by (simp add: norm_complex_def power2_eq_square)
hoelzl@56889
   896
  moreover
hoelzl@56889
   897
  have "\<bar>Re z\<bar> \<le> cmod z"
hoelzl@56889
   898
    by (simp add: norm_complex_def)
hoelzl@56889
   899
  ultimately show ?thesis
hoelzl@56889
   900
    by (simp add: Re_power2 Im_power2 complex_eq_iff real_sgn_eq
hoelzl@56889
   901
                  field_simps real_sqrt_mult[symmetric] real_sqrt_divide)
hoelzl@56889
   902
qed
hoelzl@56889
   903
hoelzl@56889
   904
lemma csqrt_eq_0 [simp]: "csqrt z = 0 \<longleftrightarrow> z = 0"
hoelzl@56889
   905
  by auto (metis power2_csqrt power_eq_0_iff)
hoelzl@56889
   906
hoelzl@56889
   907
lemma csqrt_eq_1 [simp]: "csqrt z = 1 \<longleftrightarrow> z = 1"
hoelzl@56889
   908
  by auto (metis power2_csqrt power2_eq_1_iff)
hoelzl@56889
   909
hoelzl@56889
   910
lemma csqrt_principal: "0 < Re (csqrt z) \<or> Re (csqrt z) = 0 \<and> 0 \<le> Im (csqrt z)"
hoelzl@56889
   911
  by (auto simp add: not_less cmod_plus_Re_le_0_iff Im_eq_0)
hoelzl@56889
   912
hoelzl@56889
   913
lemma Re_csqrt: "0 \<le> Re (csqrt z)"
hoelzl@56889
   914
  by (metis csqrt_principal le_less)
hoelzl@56889
   915
hoelzl@56889
   916
lemma csqrt_square:
hoelzl@56889
   917
  assumes "0 < Re b \<or> (Re b = 0 \<and> 0 \<le> Im b)"
hoelzl@56889
   918
  shows "csqrt (b^2) = b"
hoelzl@56889
   919
proof -
hoelzl@56889
   920
  have "csqrt (b^2) = b \<or> csqrt (b^2) = - b"
hoelzl@56889
   921
    unfolding power2_eq_iff[symmetric] by (simp add: power2_csqrt)
hoelzl@56889
   922
  moreover have "csqrt (b^2) \<noteq> -b \<or> b = 0"
hoelzl@56889
   923
    using csqrt_principal[of "b ^ 2"] assms by (intro disjCI notI) (auto simp: complex_eq_iff)
hoelzl@56889
   924
  ultimately show ?thesis
hoelzl@56889
   925
    by auto
hoelzl@56889
   926
qed
hoelzl@56889
   927
lp15@59746
   928
lemma csqrt_unique:
lp15@59746
   929
    "w^2 = z \<Longrightarrow> (0 < Re w \<or> Re w = 0 \<and> 0 \<le> Im w) \<Longrightarrow> csqrt z = w"
lp15@59746
   930
  by (auto simp: csqrt_square)
lp15@59746
   931
lp15@59613
   932
lemma csqrt_minus [simp]:
hoelzl@56889
   933
  assumes "Im x < 0 \<or> (Im x = 0 \<and> 0 \<le> Re x)"
hoelzl@56889
   934
  shows "csqrt (- x) = \<i> * csqrt x"
hoelzl@56889
   935
proof -
hoelzl@56889
   936
  have "csqrt ((\<i> * csqrt x)^2) = \<i> * csqrt x"
hoelzl@56889
   937
  proof (rule csqrt_square)
hoelzl@56889
   938
    have "Im (csqrt x) \<le> 0"
hoelzl@56889
   939
      using assms by (auto simp add: cmod_eq_Re mult_le_0_iff field_simps complex_Re_le_cmod)
hoelzl@56889
   940
    then show "0 < Re (\<i> * csqrt x) \<or> Re (\<i> * csqrt x) = 0 \<and> 0 \<le> Im (\<i> * csqrt x)"
hoelzl@56889
   941
      by (auto simp add: Re_csqrt simp del: csqrt.simps)
hoelzl@56889
   942
  qed
hoelzl@56889
   943
  also have "(\<i> * csqrt x)^2 = - x"
lp15@59746
   944
    by (simp add: power_mult_distrib)
hoelzl@56889
   945
  finally show ?thesis .
hoelzl@56889
   946
qed
huffman@44844
   947
wenzelm@60758
   948
text \<open>Legacy theorem names\<close>
huffman@44065
   949
huffman@44065
   950
lemmas expand_complex_eq = complex_eq_iff
huffman@44065
   951
lemmas complex_Re_Im_cancel_iff = complex_eq_iff
huffman@44065
   952
lemmas complex_equality = complex_eqI
hoelzl@56889
   953
lemmas cmod_def = norm_complex_def
hoelzl@56889
   954
lemmas complex_norm_def = norm_complex_def
hoelzl@56889
   955
lemmas complex_divide_def = divide_complex_def
hoelzl@56889
   956
hoelzl@56889
   957
lemma legacy_Complex_simps:
hoelzl@56889
   958
  shows Complex_eq_0: "Complex a b = 0 \<longleftrightarrow> a = 0 \<and> b = 0"
hoelzl@56889
   959
    and complex_add: "Complex a b + Complex c d = Complex (a + c) (b + d)"
hoelzl@56889
   960
    and complex_minus: "- (Complex a b) = Complex (- a) (- b)"
hoelzl@56889
   961
    and complex_diff: "Complex a b - Complex c d = Complex (a - c) (b - d)"
hoelzl@56889
   962
    and Complex_eq_1: "Complex a b = 1 \<longleftrightarrow> a = 1 \<and> b = 0"
hoelzl@56889
   963
    and Complex_eq_neg_1: "Complex a b = - 1 \<longleftrightarrow> a = - 1 \<and> b = 0"
hoelzl@56889
   964
    and complex_mult: "Complex a b * Complex c d = Complex (a * c - b * d) (a * d + b * c)"
hoelzl@56889
   965
    and complex_inverse: "inverse (Complex a b) = Complex (a / (a\<^sup>2 + b\<^sup>2)) (- b / (a\<^sup>2 + b\<^sup>2))"
hoelzl@56889
   966
    and Complex_eq_numeral: "Complex a b = numeral w \<longleftrightarrow> a = numeral w \<and> b = 0"
hoelzl@56889
   967
    and Complex_eq_neg_numeral: "Complex a b = - numeral w \<longleftrightarrow> a = - numeral w \<and> b = 0"
hoelzl@56889
   968
    and complex_scaleR: "scaleR r (Complex a b) = Complex (r * a) (r * b)"
hoelzl@56889
   969
    and Complex_eq_i: "(Complex x y = ii) = (x = 0 \<and> y = 1)"
hoelzl@56889
   970
    and i_mult_Complex: "ii * Complex a b = Complex (- b) a"
hoelzl@56889
   971
    and Complex_mult_i: "Complex a b * ii = Complex (- b) a"
hoelzl@56889
   972
    and i_complex_of_real: "ii * complex_of_real r = Complex 0 r"
hoelzl@56889
   973
    and complex_of_real_i: "complex_of_real r * ii = Complex 0 r"
hoelzl@56889
   974
    and Complex_add_complex_of_real: "Complex x y + complex_of_real r = Complex (x+r) y"
hoelzl@56889
   975
    and complex_of_real_add_Complex: "complex_of_real r + Complex x y = Complex (r+x) y"
hoelzl@56889
   976
    and Complex_mult_complex_of_real: "Complex x y * complex_of_real r = Complex (x*r) (y*r)"
hoelzl@56889
   977
    and complex_of_real_mult_Complex: "complex_of_real r * Complex x y = Complex (r*x) (r*y)"
hoelzl@56889
   978
    and complex_eq_cancel_iff2: "(Complex x y = complex_of_real xa) = (x = xa & y = 0)"
hoelzl@56889
   979
    and complex_cn: "cnj (Complex a b) = Complex a (- b)"
hoelzl@56889
   980
    and Complex_setsum': "setsum (%x. Complex (f x) 0) s = Complex (setsum f s) 0"
hoelzl@56889
   981
    and Complex_setsum: "Complex (setsum f s) 0 = setsum (%x. Complex (f x) 0) s"
hoelzl@56889
   982
    and complex_of_real_def: "complex_of_real r = Complex r 0"
hoelzl@56889
   983
    and complex_norm: "cmod (Complex x y) = sqrt (x\<^sup>2 + y\<^sup>2)"
hoelzl@56889
   984
  by (simp_all add: norm_complex_def field_simps complex_eq_iff Re_divide Im_divide del: Complex_eq)
hoelzl@56889
   985
hoelzl@56889
   986
lemma Complex_in_Reals: "Complex x 0 \<in> \<real>"
hoelzl@56889
   987
  by (metis Reals_of_real complex_of_real_def)
huffman@44065
   988
paulson@13957
   989
end