src/HOL/Complex.thy
author wenzelm
Mon Apr 25 16:09:26 2016 +0200 (2016-04-25)
changeset 63040 eb4ddd18d635
parent 62620 d21dab28b3f9
child 63114 27afe7af7379
permissions -rw-r--r--
eliminated old 'def';
tuned comments;
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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 \<open>codatatype\<close> command to define the type of complex numbers. This allows us to use
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\<open>primcorec\<close> 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 [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]:
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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 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 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 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 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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   322
  by (simp add: norm_complex_def)
hoelzl@56889
   323
hoelzl@56889
   324
lemma cmod_eq_Im: "Re z = 0 \<Longrightarrow> cmod z = \<bar>Im z\<bar>"
hoelzl@56889
   325
  by (simp add: norm_complex_def)
huffman@44724
   326
hoelzl@56889
   327
lemma cmod_power2: "cmod z ^ 2 = (Re z)^2 + (Im z)^2"
hoelzl@56889
   328
  by (simp add: norm_complex_def)
hoelzl@56889
   329
hoelzl@56889
   330
lemma cmod_plus_Re_le_0_iff: "cmod z + Re z \<le> 0 \<longleftrightarrow> Re z = - cmod z"
hoelzl@56889
   331
  using abs_Re_le_cmod[of z] by auto
hoelzl@56889
   332
lp15@62379
   333
lemma cmod_Re_le_iff: "Im x = Im y \<Longrightarrow> cmod x \<le> cmod y \<longleftrightarrow> abs (Re x) \<le> abs (Re y)"
lp15@62379
   334
  by (metis add.commute add_le_cancel_left norm_complex_def real_sqrt_abs real_sqrt_le_iff)
lp15@62379
   335
lp15@62379
   336
lemma cmod_Im_le_iff: "Re x = Re y \<Longrightarrow> cmod x \<le> cmod y \<longleftrightarrow> abs (Im x) \<le> abs (Im y)"
lp15@62379
   337
  by (metis add_le_cancel_left norm_complex_def real_sqrt_abs real_sqrt_le_iff)
lp15@62379
   338
hoelzl@56889
   339
lemma Im_eq_0: "\<bar>Re z\<bar> = cmod z \<Longrightarrow> Im z = 0"
hoelzl@56889
   340
  by (subst (asm) power_eq_iff_eq_base[symmetric, where n=2])
hoelzl@56889
   341
     (auto simp add: norm_complex_def)
hoelzl@56369
   342
hoelzl@56369
   343
lemma abs_sqrt_wlog:
hoelzl@56369
   344
  fixes x::"'a::linordered_idom"
hoelzl@56369
   345
  assumes "\<And>x::'a. x \<ge> 0 \<Longrightarrow> P x (x\<^sup>2)" shows "P \<bar>x\<bar> (x\<^sup>2)"
hoelzl@56369
   346
by (metis abs_ge_zero assms power2_abs)
hoelzl@56369
   347
hoelzl@56369
   348
lemma complex_abs_le_norm: "\<bar>Re z\<bar> + \<bar>Im z\<bar> \<le> sqrt 2 * norm z"
hoelzl@56889
   349
  unfolding norm_complex_def
hoelzl@56369
   350
  apply (rule abs_sqrt_wlog [where x="Re z"])
hoelzl@56369
   351
  apply (rule abs_sqrt_wlog [where x="Im z"])
hoelzl@56369
   352
  apply (rule power2_le_imp_le)
haftmann@57512
   353
  apply (simp_all add: power2_sum add.commute sum_squares_bound real_sqrt_mult [symmetric])
hoelzl@56369
   354
  done
hoelzl@56369
   355
lp15@59741
   356
lemma complex_unit_circle: "z \<noteq> 0 \<Longrightarrow> (Re z / cmod z)\<^sup>2 + (Im z / cmod z)\<^sup>2 = 1"
lp15@59741
   357
  by (simp add: norm_complex_def divide_simps complex_eq_iff)
lp15@59741
   358
hoelzl@56369
   359
wenzelm@60758
   360
text \<open>Properties of complex signum.\<close>
huffman@44843
   361
huffman@44843
   362
lemma sgn_eq: "sgn z = z / complex_of_real (cmod z)"
haftmann@57512
   363
  by (simp add: sgn_div_norm divide_inverse scaleR_conv_of_real mult.commute)
huffman@44843
   364
huffman@44843
   365
lemma Re_sgn [simp]: "Re(sgn z) = Re(z)/cmod z"
huffman@44843
   366
  by (simp add: complex_sgn_def divide_inverse)
huffman@44843
   367
huffman@44843
   368
lemma Im_sgn [simp]: "Im(sgn z) = Im(z)/cmod z"
huffman@44843
   369
  by (simp add: complex_sgn_def divide_inverse)
huffman@44843
   370
paulson@14354
   371
wenzelm@60758
   372
subsection \<open>Completeness of the Complexes\<close>
huffman@23123
   373
huffman@44290
   374
lemma bounded_linear_Re: "bounded_linear Re"
hoelzl@56889
   375
  by (rule bounded_linear_intro [where K=1], simp_all add: norm_complex_def)
huffman@44290
   376
huffman@44290
   377
lemma bounded_linear_Im: "bounded_linear Im"
hoelzl@56889
   378
  by (rule bounded_linear_intro [where K=1], simp_all add: norm_complex_def)
huffman@23123
   379
huffman@44290
   380
lemmas Cauchy_Re = bounded_linear.Cauchy [OF bounded_linear_Re]
huffman@44290
   381
lemmas Cauchy_Im = bounded_linear.Cauchy [OF bounded_linear_Im]
hoelzl@56381
   382
lemmas tendsto_Re [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_Re]
hoelzl@56381
   383
lemmas tendsto_Im [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_Im]
hoelzl@56381
   384
lemmas isCont_Re [simp] = bounded_linear.isCont [OF bounded_linear_Re]
hoelzl@56381
   385
lemmas isCont_Im [simp] = bounded_linear.isCont [OF bounded_linear_Im]
hoelzl@56381
   386
lemmas continuous_Re [simp] = bounded_linear.continuous [OF bounded_linear_Re]
hoelzl@56381
   387
lemmas continuous_Im [simp] = bounded_linear.continuous [OF bounded_linear_Im]
hoelzl@56381
   388
lemmas continuous_on_Re [continuous_intros] = bounded_linear.continuous_on[OF bounded_linear_Re]
hoelzl@56381
   389
lemmas continuous_on_Im [continuous_intros] = bounded_linear.continuous_on[OF bounded_linear_Im]
hoelzl@56381
   390
lemmas has_derivative_Re [derivative_intros] = bounded_linear.has_derivative[OF bounded_linear_Re]
hoelzl@56381
   391
lemmas has_derivative_Im [derivative_intros] = bounded_linear.has_derivative[OF bounded_linear_Im]
hoelzl@56381
   392
lemmas sums_Re = bounded_linear.sums [OF bounded_linear_Re]
hoelzl@56381
   393
lemmas sums_Im = bounded_linear.sums [OF bounded_linear_Im]
hoelzl@56369
   394
huffman@36825
   395
lemma tendsto_Complex [tendsto_intros]:
wenzelm@61973
   396
  "(f \<longlongrightarrow> a) F \<Longrightarrow> (g \<longlongrightarrow> b) F \<Longrightarrow> ((\<lambda>x. Complex (f x) (g x)) \<longlongrightarrow> Complex a b) F"
hoelzl@56889
   397
  by (auto intro!: tendsto_intros)
hoelzl@56369
   398
hoelzl@56369
   399
lemma tendsto_complex_iff:
wenzelm@61973
   400
  "(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
   401
proof safe
wenzelm@61973
   402
  assume "((\<lambda>x. Re (f x)) \<longlongrightarrow> Re x) F" "((\<lambda>x. Im (f x)) \<longlongrightarrow> Im x) F"
wenzelm@61973
   403
  from tendsto_Complex[OF this] show "(f \<longlongrightarrow> x) F"
hoelzl@56889
   404
    unfolding complex.collapse .
hoelzl@56889
   405
qed (auto intro: tendsto_intros)
hoelzl@56369
   406
hoelzl@57259
   407
lemma continuous_complex_iff: "continuous F f \<longleftrightarrow>
hoelzl@57259
   408
    continuous F (\<lambda>x. Re (f x)) \<and> continuous F (\<lambda>x. Im (f x))"
hoelzl@57259
   409
  unfolding continuous_def tendsto_complex_iff ..
hoelzl@57259
   410
hoelzl@57259
   411
lemma has_vector_derivative_complex_iff: "(f has_vector_derivative x) F \<longleftrightarrow>
hoelzl@57259
   412
    ((\<lambda>x. Re (f x)) has_field_derivative (Re x)) F \<and>
hoelzl@57259
   413
    ((\<lambda>x. Im (f x)) has_field_derivative (Im x)) F"
hoelzl@57259
   414
  unfolding has_vector_derivative_def has_field_derivative_def has_derivative_def tendsto_complex_iff
hoelzl@57259
   415
  by (simp add: field_simps bounded_linear_scaleR_left bounded_linear_mult_right)
hoelzl@57259
   416
hoelzl@57259
   417
lemma has_field_derivative_Re[derivative_intros]:
hoelzl@57259
   418
  "(f has_vector_derivative D) F \<Longrightarrow> ((\<lambda>x. Re (f x)) has_field_derivative (Re D)) F"
hoelzl@57259
   419
  unfolding has_vector_derivative_complex_iff by safe
hoelzl@57259
   420
hoelzl@57259
   421
lemma has_field_derivative_Im[derivative_intros]:
hoelzl@57259
   422
  "(f has_vector_derivative D) F \<Longrightarrow> ((\<lambda>x. Im (f x)) has_field_derivative (Im D)) F"
hoelzl@57259
   423
  unfolding has_vector_derivative_complex_iff by safe
hoelzl@57259
   424
huffman@23123
   425
instance complex :: banach
huffman@23123
   426
proof
huffman@23123
   427
  fix X :: "nat \<Rightarrow> complex"
huffman@23123
   428
  assume X: "Cauchy X"
wenzelm@61969
   429
  then have "(\<lambda>n. Complex (Re (X n)) (Im (X n))) \<longlonglongrightarrow> Complex (lim (\<lambda>n. Re (X n))) (lim (\<lambda>n. Im (X n)))"
hoelzl@56889
   430
    by (intro tendsto_Complex convergent_LIMSEQ_iff[THEN iffD1] Cauchy_convergent_iff[THEN iffD1] Cauchy_Re Cauchy_Im)
hoelzl@56889
   431
  then show "convergent X"
hoelzl@56889
   432
    unfolding complex.collapse by (rule convergentI)
huffman@23123
   433
qed
huffman@23123
   434
lp15@56238
   435
declare
hoelzl@56381
   436
  DERIV_power[where 'a=complex, unfolded of_nat_def[symmetric], derivative_intros]
lp15@56238
   437
wenzelm@60758
   438
subsection \<open>Complex Conjugation\<close>
huffman@23125
   439
hoelzl@56889
   440
primcorec cnj :: "complex \<Rightarrow> complex" where
hoelzl@56889
   441
  "Re (cnj z) = Re z"
hoelzl@56889
   442
| "Im (cnj z) = - Im z"
huffman@23125
   443
huffman@23125
   444
lemma complex_cnj_cancel_iff [simp]: "(cnj x = cnj y) = (x = y)"
huffman@44724
   445
  by (simp add: complex_eq_iff)
huffman@23125
   446
huffman@23125
   447
lemma complex_cnj_cnj [simp]: "cnj (cnj z) = z"
hoelzl@56889
   448
  by (simp add: complex_eq_iff)
huffman@23125
   449
huffman@23125
   450
lemma complex_cnj_zero [simp]: "cnj 0 = 0"
huffman@44724
   451
  by (simp add: complex_eq_iff)
huffman@23125
   452
huffman@23125
   453
lemma complex_cnj_zero_iff [iff]: "(cnj z = 0) = (z = 0)"
huffman@44724
   454
  by (simp add: complex_eq_iff)
huffman@23125
   455
hoelzl@56889
   456
lemma complex_cnj_add [simp]: "cnj (x + y) = cnj x + cnj y"
huffman@44724
   457
  by (simp add: complex_eq_iff)
huffman@23125
   458
hoelzl@56889
   459
lemma cnj_setsum [simp]: "cnj (setsum f s) = (\<Sum>x\<in>s. cnj (f x))"
hoelzl@56889
   460
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   461
hoelzl@56889
   462
lemma complex_cnj_diff [simp]: "cnj (x - y) = cnj x - cnj y"
huffman@44724
   463
  by (simp add: complex_eq_iff)
huffman@23125
   464
hoelzl@56889
   465
lemma complex_cnj_minus [simp]: "cnj (- x) = - cnj x"
huffman@44724
   466
  by (simp add: complex_eq_iff)
huffman@23125
   467
huffman@23125
   468
lemma complex_cnj_one [simp]: "cnj 1 = 1"
huffman@44724
   469
  by (simp add: complex_eq_iff)
huffman@23125
   470
hoelzl@56889
   471
lemma complex_cnj_mult [simp]: "cnj (x * y) = cnj x * cnj y"
huffman@44724
   472
  by (simp add: complex_eq_iff)
huffman@23125
   473
hoelzl@56889
   474
lemma cnj_setprod [simp]: "cnj (setprod f s) = (\<Prod>x\<in>s. cnj (f x))"
hoelzl@56889
   475
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   476
hoelzl@56889
   477
lemma complex_cnj_inverse [simp]: "cnj (inverse x) = inverse (cnj x)"
hoelzl@56889
   478
  by (simp add: complex_eq_iff)
paulson@14323
   479
hoelzl@56889
   480
lemma complex_cnj_divide [simp]: "cnj (x / y) = cnj x / cnj y"
hoelzl@56889
   481
  by (simp add: divide_complex_def)
huffman@23125
   482
hoelzl@56889
   483
lemma complex_cnj_power [simp]: "cnj (x ^ n) = cnj x ^ n"
hoelzl@56889
   484
  by (induct n) simp_all
huffman@23125
   485
huffman@23125
   486
lemma complex_cnj_of_nat [simp]: "cnj (of_nat n) = of_nat n"
huffman@44724
   487
  by (simp add: complex_eq_iff)
huffman@23125
   488
huffman@23125
   489
lemma complex_cnj_of_int [simp]: "cnj (of_int z) = of_int z"
huffman@44724
   490
  by (simp add: complex_eq_iff)
huffman@23125
   491
huffman@47108
   492
lemma complex_cnj_numeral [simp]: "cnj (numeral w) = numeral w"
huffman@47108
   493
  by (simp add: complex_eq_iff)
huffman@47108
   494
haftmann@54489
   495
lemma complex_cnj_neg_numeral [simp]: "cnj (- numeral w) = - numeral w"
huffman@44724
   496
  by (simp add: complex_eq_iff)
huffman@23125
   497
hoelzl@56889
   498
lemma complex_cnj_scaleR [simp]: "cnj (scaleR r x) = scaleR r (cnj x)"
huffman@44724
   499
  by (simp add: complex_eq_iff)
huffman@23125
   500
huffman@23125
   501
lemma complex_mod_cnj [simp]: "cmod (cnj z) = cmod z"
hoelzl@56889
   502
  by (simp add: norm_complex_def)
paulson@14323
   503
huffman@23125
   504
lemma complex_cnj_complex_of_real [simp]: "cnj (of_real x) = of_real x"
huffman@44724
   505
  by (simp add: complex_eq_iff)
huffman@23125
   506
huffman@23125
   507
lemma complex_cnj_i [simp]: "cnj ii = - ii"
huffman@44724
   508
  by (simp add: complex_eq_iff)
huffman@23125
   509
huffman@23125
   510
lemma complex_add_cnj: "z + cnj z = complex_of_real (2 * Re z)"
huffman@44724
   511
  by (simp add: complex_eq_iff)
huffman@23125
   512
huffman@23125
   513
lemma complex_diff_cnj: "z - cnj z = complex_of_real (2 * Im z) * ii"
huffman@44724
   514
  by (simp add: complex_eq_iff)
paulson@14354
   515
wenzelm@53015
   516
lemma complex_mult_cnj: "z * cnj z = complex_of_real ((Re z)\<^sup>2 + (Im z)\<^sup>2)"
huffman@44724
   517
  by (simp add: complex_eq_iff power2_eq_square)
huffman@23125
   518
wenzelm@53015
   519
lemma complex_mod_mult_cnj: "cmod (z * cnj z) = (cmod z)\<^sup>2"
huffman@44724
   520
  by (simp add: norm_mult power2_eq_square)
huffman@23125
   521
huffman@44827
   522
lemma complex_mod_sqrt_Re_mult_cnj: "cmod z = sqrt (Re (z * cnj z))"
hoelzl@56889
   523
  by (simp add: norm_complex_def power2_eq_square)
huffman@44827
   524
huffman@44827
   525
lemma complex_In_mult_cnj_zero [simp]: "Im (z * cnj z) = 0"
huffman@44827
   526
  by simp
huffman@44827
   527
eberlm@61531
   528
lemma complex_cnj_fact [simp]: "cnj (fact n) = fact n"
eberlm@61531
   529
  by (subst of_nat_fact [symmetric], subst complex_cnj_of_nat) simp
eberlm@61531
   530
eberlm@61531
   531
lemma complex_cnj_pochhammer [simp]: "cnj (pochhammer z n) = pochhammer (cnj z) n"
eberlm@61531
   532
  by (induction n arbitrary: z) (simp_all add: pochhammer_rec)
eberlm@61531
   533
huffman@44290
   534
lemma bounded_linear_cnj: "bounded_linear cnj"
huffman@44127
   535
  using complex_cnj_add complex_cnj_scaleR
huffman@44127
   536
  by (rule bounded_linear_intro [where K=1], simp)
paulson@14354
   537
hoelzl@56381
   538
lemmas tendsto_cnj [tendsto_intros] = bounded_linear.tendsto [OF bounded_linear_cnj]
hoelzl@56381
   539
lemmas isCont_cnj [simp] = bounded_linear.isCont [OF bounded_linear_cnj]
hoelzl@56381
   540
lemmas continuous_cnj [simp, continuous_intros] = bounded_linear.continuous [OF bounded_linear_cnj]
hoelzl@56381
   541
lemmas continuous_on_cnj [simp, continuous_intros] = bounded_linear.continuous_on [OF bounded_linear_cnj]
hoelzl@56381
   542
lemmas has_derivative_cnj [simp, derivative_intros] = bounded_linear.has_derivative [OF bounded_linear_cnj]
huffman@44290
   543
wenzelm@61973
   544
lemma lim_cnj: "((\<lambda>x. cnj(f x)) \<longlongrightarrow> cnj l) F \<longleftrightarrow> (f \<longlongrightarrow> l) F"
hoelzl@56889
   545
  by (simp add: tendsto_iff dist_complex_def complex_cnj_diff [symmetric] del: complex_cnj_diff)
hoelzl@56369
   546
hoelzl@56369
   547
lemma sums_cnj: "((\<lambda>x. cnj(f x)) sums cnj l) \<longleftrightarrow> (f sums l)"
hoelzl@56889
   548
  by (simp add: sums_def lim_cnj cnj_setsum [symmetric] del: cnj_setsum)
hoelzl@56369
   549
paulson@14354
   550
wenzelm@60758
   551
subsection\<open>Basic Lemmas\<close>
lp15@55734
   552
lp15@55734
   553
lemma complex_eq_0: "z=0 \<longleftrightarrow> (Re z)\<^sup>2 + (Im z)\<^sup>2 = 0"
hoelzl@56889
   554
  by (metis zero_complex.sel complex_eqI sum_power2_eq_zero_iff)
lp15@55734
   555
lp15@55734
   556
lemma complex_neq_0: "z\<noteq>0 \<longleftrightarrow> (Re z)\<^sup>2 + (Im z)\<^sup>2 > 0"
hoelzl@56889
   557
  by (metis complex_eq_0 less_numeral_extra(3) sum_power2_gt_zero_iff)
lp15@55734
   558
lp15@55734
   559
lemma complex_norm_square: "of_real ((norm z)\<^sup>2) = z * cnj z"
hoelzl@56889
   560
by (cases z)
hoelzl@56889
   561
   (auto simp: complex_eq_iff norm_complex_def power2_eq_square[symmetric] of_real_power[symmetric]
hoelzl@56889
   562
         simp del: of_real_power)
lp15@55734
   563
paulson@61104
   564
lemma complex_div_cnj: "a / b = (a * cnj b) / (norm b)^2"
paulson@61104
   565
  using complex_norm_square by auto
paulson@61104
   566
lp15@59741
   567
lemma Re_complex_div_eq_0: "Re (a / b) = 0 \<longleftrightarrow> Re (a * cnj b) = 0"
hoelzl@56889
   568
  by (auto simp add: Re_divide)
lp15@59613
   569
lp15@59741
   570
lemma Im_complex_div_eq_0: "Im (a / b) = 0 \<longleftrightarrow> Im (a * cnj b) = 0"
hoelzl@56889
   571
  by (auto simp add: Im_divide)
hoelzl@56889
   572
lp15@59613
   573
lemma complex_div_gt_0:
hoelzl@56889
   574
  "(Re (a / b) > 0 \<longleftrightarrow> Re (a * cnj b) > 0) \<and> (Im (a / b) > 0 \<longleftrightarrow> Im (a * cnj b) > 0)"
hoelzl@56889
   575
proof cases
hoelzl@56889
   576
  assume "b = 0" then show ?thesis by auto
lp15@55734
   577
next
hoelzl@56889
   578
  assume "b \<noteq> 0"
hoelzl@56889
   579
  then have "0 < (Re b)\<^sup>2 + (Im b)\<^sup>2"
hoelzl@56889
   580
    by (simp add: complex_eq_iff sum_power2_gt_zero_iff)
hoelzl@56889
   581
  then show ?thesis
hoelzl@56889
   582
    by (simp add: Re_divide Im_divide zero_less_divide_iff)
lp15@55734
   583
qed
lp15@55734
   584
lp15@59741
   585
lemma Re_complex_div_gt_0: "Re (a / b) > 0 \<longleftrightarrow> Re (a * cnj b) > 0"
lp15@59741
   586
  and Im_complex_div_gt_0: "Im (a / b) > 0 \<longleftrightarrow> Im (a * cnj b) > 0"
hoelzl@56889
   587
  using complex_div_gt_0 by auto
lp15@55734
   588
lp15@59741
   589
lemma Re_complex_div_ge_0: "Re(a / b) \<ge> 0 \<longleftrightarrow> Re(a * cnj b) \<ge> 0"
lp15@59741
   590
  by (metis le_less Re_complex_div_eq_0 Re_complex_div_gt_0)
lp15@55734
   591
lp15@59741
   592
lemma Im_complex_div_ge_0: "Im(a / b) \<ge> 0 \<longleftrightarrow> Im(a * cnj b) \<ge> 0"
lp15@59741
   593
  by (metis Im_complex_div_eq_0 Im_complex_div_gt_0 le_less)
lp15@55734
   594
lp15@59741
   595
lemma Re_complex_div_lt_0: "Re(a / b) < 0 \<longleftrightarrow> Re(a * cnj b) < 0"
lp15@59741
   596
  by (metis less_asym neq_iff Re_complex_div_eq_0 Re_complex_div_gt_0)
lp15@55734
   597
lp15@59741
   598
lemma Im_complex_div_lt_0: "Im(a / b) < 0 \<longleftrightarrow> Im(a * cnj b) < 0"
lp15@59741
   599
  by (metis Im_complex_div_eq_0 Im_complex_div_gt_0 less_asym neq_iff)
lp15@55734
   600
lp15@59741
   601
lemma Re_complex_div_le_0: "Re(a / b) \<le> 0 \<longleftrightarrow> Re(a * cnj b) \<le> 0"
lp15@59741
   602
  by (metis not_le Re_complex_div_gt_0)
lp15@55734
   603
lp15@59741
   604
lemma Im_complex_div_le_0: "Im(a / b) \<le> 0 \<longleftrightarrow> Im(a * cnj b) \<le> 0"
lp15@59741
   605
  by (metis Im_complex_div_gt_0 not_le)
lp15@55734
   606
paulson@61104
   607
lemma Re_divide_of_real [simp]: "Re (z / of_real r) = Re z / r"
paulson@61104
   608
  by (simp add: Re_divide power2_eq_square)
paulson@61104
   609
paulson@61104
   610
lemma Im_divide_of_real [simp]: "Im (z / of_real r) = Im z / r"
paulson@61104
   611
  by (simp add: Im_divide power2_eq_square)
paulson@61104
   612
paulson@61104
   613
lemma Re_divide_Reals: "r \<in> Reals \<Longrightarrow> Re (z / r) = Re z / Re r"
paulson@61104
   614
  by (metis Re_divide_of_real of_real_Re)
paulson@61104
   615
paulson@61104
   616
lemma Im_divide_Reals: "r \<in> Reals \<Longrightarrow> Im (z / r) = Im z / Re r"
paulson@61104
   617
  by (metis Im_divide_of_real of_real_Re)
paulson@61104
   618
hoelzl@56889
   619
lemma Re_setsum[simp]: "Re (setsum f s) = (\<Sum>x\<in>s. Re (f x))"
hoelzl@56369
   620
  by (induct s rule: infinite_finite_induct) auto
lp15@55734
   621
hoelzl@56889
   622
lemma Im_setsum[simp]: "Im (setsum f s) = (\<Sum>x\<in>s. Im(f x))"
hoelzl@56369
   623
  by (induct s rule: infinite_finite_induct) auto
hoelzl@56369
   624
hoelzl@56369
   625
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
   626
  unfolding sums_def tendsto_complex_iff Im_setsum Re_setsum ..
lp15@59613
   627
hoelzl@56369
   628
lemma summable_complex_iff: "summable f \<longleftrightarrow> summable (\<lambda>x. Re (f x)) \<and>  summable (\<lambda>x. Im (f x))"
hoelzl@56889
   629
  unfolding summable_def sums_complex_iff[abs_def] by (metis complex.sel)
hoelzl@56369
   630
hoelzl@56369
   631
lemma summable_complex_of_real [simp]: "summable (\<lambda>n. complex_of_real (f n)) \<longleftrightarrow> summable f"
hoelzl@56369
   632
  unfolding summable_complex_iff by simp
hoelzl@56369
   633
hoelzl@56369
   634
lemma summable_Re: "summable f \<Longrightarrow> summable (\<lambda>x. Re (f x))"
hoelzl@56369
   635
  unfolding summable_complex_iff by blast
hoelzl@56369
   636
hoelzl@56369
   637
lemma summable_Im: "summable f \<Longrightarrow> summable (\<lambda>x. Im (f x))"
hoelzl@56369
   638
  unfolding summable_complex_iff by blast
lp15@56217
   639
paulson@61104
   640
lemma complex_is_Nat_iff: "z \<in> \<nat> \<longleftrightarrow> Im z = 0 \<and> (\<exists>i. Re z = of_nat i)"
paulson@61104
   641
  by (auto simp: Nats_def complex_eq_iff)
paulson@61104
   642
paulson@61104
   643
lemma complex_is_Int_iff: "z \<in> \<int> \<longleftrightarrow> Im z = 0 \<and> (\<exists>i. Re z = of_int i)"
paulson@61104
   644
  by (auto simp: Ints_def complex_eq_iff)
paulson@61104
   645
hoelzl@56889
   646
lemma complex_is_Real_iff: "z \<in> \<real> \<longleftrightarrow> Im z = 0"
hoelzl@56889
   647
  by (auto simp: Reals_def complex_eq_iff)
lp15@55734
   648
lp15@55734
   649
lemma Reals_cnj_iff: "z \<in> \<real> \<longleftrightarrow> cnj z = z"
hoelzl@56889
   650
  by (auto simp: complex_is_Real_iff complex_eq_iff)
lp15@55734
   651
wenzelm@61944
   652
lemma in_Reals_norm: "z \<in> \<real> \<Longrightarrow> norm z = \<bar>Re z\<bar>"
hoelzl@56889
   653
  by (simp add: complex_is_Real_iff norm_complex_def)
hoelzl@56369
   654
hoelzl@56369
   655
lemma series_comparison_complex:
hoelzl@56369
   656
  fixes f:: "nat \<Rightarrow> 'a::banach"
hoelzl@56369
   657
  assumes sg: "summable g"
hoelzl@56369
   658
     and "\<And>n. g n \<in> \<real>" "\<And>n. Re (g n) \<ge> 0"
hoelzl@56369
   659
     and fg: "\<And>n. n \<ge> N \<Longrightarrow> norm(f n) \<le> norm(g n)"
hoelzl@56369
   660
  shows "summable f"
hoelzl@56369
   661
proof -
hoelzl@56369
   662
  have g: "\<And>n. cmod (g n) = Re (g n)" using assms
hoelzl@56369
   663
    by (metis abs_of_nonneg in_Reals_norm)
hoelzl@56369
   664
  show ?thesis
hoelzl@56369
   665
    apply (rule summable_comparison_test' [where g = "\<lambda>n. norm (g n)" and N=N])
hoelzl@56369
   666
    using sg
hoelzl@56369
   667
    apply (auto simp: summable_def)
hoelzl@56369
   668
    apply (rule_tac x="Re s" in exI)
hoelzl@56369
   669
    apply (auto simp: g sums_Re)
hoelzl@56369
   670
    apply (metis fg g)
hoelzl@56369
   671
    done
hoelzl@56369
   672
qed
lp15@55734
   673
wenzelm@60758
   674
subsection\<open>Polar Form for Complex Numbers\<close>
lp15@59746
   675
lp15@62620
   676
lemma complex_unimodular_polar:
lp15@62620
   677
  assumes "(norm z = 1)"
lp15@62620
   678
  obtains t where "0 \<le> t" "t < 2*pi" "z = Complex (cos t) (sin t)"
lp15@62620
   679
by (metis cmod_power2 one_power2 complex_surj sincos_total_2pi [of "Re z" "Im z"] assms)
paulson@14323
   680
wenzelm@60758
   681
subsubsection \<open>$\cos \theta + i \sin \theta$\<close>
huffman@20557
   682
hoelzl@56889
   683
primcorec cis :: "real \<Rightarrow> complex" where
hoelzl@56889
   684
  "Re (cis a) = cos a"
hoelzl@56889
   685
| "Im (cis a) = sin a"
huffman@44827
   686
huffman@44827
   687
lemma cis_zero [simp]: "cis 0 = 1"
hoelzl@56889
   688
  by (simp add: complex_eq_iff)
huffman@44827
   689
huffman@44828
   690
lemma norm_cis [simp]: "norm (cis a) = 1"
hoelzl@56889
   691
  by (simp add: norm_complex_def)
huffman@44828
   692
huffman@44828
   693
lemma sgn_cis [simp]: "sgn (cis a) = cis a"
huffman@44828
   694
  by (simp add: sgn_div_norm)
huffman@44828
   695
huffman@44828
   696
lemma cis_neq_zero [simp]: "cis a \<noteq> 0"
huffman@44828
   697
  by (metis norm_cis norm_zero zero_neq_one)
huffman@44828
   698
huffman@44827
   699
lemma cis_mult: "cis a * cis b = cis (a + b)"
hoelzl@56889
   700
  by (simp add: complex_eq_iff cos_add sin_add)
huffman@44827
   701
huffman@44827
   702
lemma DeMoivre: "(cis a) ^ n = cis (real n * a)"
lp15@61609
   703
  by (induct n, simp_all add: of_nat_Suc algebra_simps cis_mult)
huffman@44827
   704
huffman@44827
   705
lemma cis_inverse [simp]: "inverse(cis a) = cis (-a)"
hoelzl@56889
   706
  by (simp add: complex_eq_iff)
huffman@44827
   707
huffman@44827
   708
lemma cis_divide: "cis a / cis b = cis (a - b)"
hoelzl@56889
   709
  by (simp add: divide_complex_def cis_mult)
huffman@44827
   710
huffman@44827
   711
lemma cos_n_Re_cis_pow_n: "cos (real n * a) = Re(cis a ^ n)"
huffman@44827
   712
  by (auto simp add: DeMoivre)
huffman@44827
   713
huffman@44827
   714
lemma sin_n_Im_cis_pow_n: "sin (real n * a) = Im(cis a ^ n)"
huffman@44827
   715
  by (auto simp add: DeMoivre)
huffman@44827
   716
hoelzl@56889
   717
lemma cis_pi: "cis pi = -1"
hoelzl@56889
   718
  by (simp add: complex_eq_iff)
hoelzl@56889
   719
wenzelm@60758
   720
subsubsection \<open>$r(\cos \theta + i \sin \theta)$\<close>
huffman@44715
   721
hoelzl@56889
   722
definition rcis :: "real \<Rightarrow> real \<Rightarrow> complex" where
huffman@20557
   723
  "rcis r a = complex_of_real r * cis a"
huffman@20557
   724
huffman@44827
   725
lemma Re_rcis [simp]: "Re(rcis r a) = r * cos a"
huffman@44828
   726
  by (simp add: rcis_def)
huffman@44827
   727
huffman@44827
   728
lemma Im_rcis [simp]: "Im(rcis r a) = r * sin a"
huffman@44828
   729
  by (simp add: rcis_def)
huffman@44827
   730
huffman@44827
   731
lemma rcis_Ex: "\<exists>r a. z = rcis r a"
huffman@44828
   732
  by (simp add: complex_eq_iff polar_Ex)
huffman@44827
   733
wenzelm@61944
   734
lemma complex_mod_rcis [simp]: "cmod (rcis r a) = \<bar>r\<bar>"
huffman@44828
   735
  by (simp add: rcis_def norm_mult)
huffman@44827
   736
huffman@44827
   737
lemma cis_rcis_eq: "cis a = rcis 1 a"
huffman@44827
   738
  by (simp add: rcis_def)
huffman@44827
   739
huffman@44827
   740
lemma rcis_mult: "rcis r1 a * rcis r2 b = rcis (r1*r2) (a + b)"
huffman@44828
   741
  by (simp add: rcis_def cis_mult)
huffman@44827
   742
huffman@44827
   743
lemma rcis_zero_mod [simp]: "rcis 0 a = 0"
huffman@44827
   744
  by (simp add: rcis_def)
huffman@44827
   745
huffman@44827
   746
lemma rcis_zero_arg [simp]: "rcis r 0 = complex_of_real r"
huffman@44827
   747
  by (simp add: rcis_def)
huffman@44827
   748
huffman@44828
   749
lemma rcis_eq_zero_iff [simp]: "rcis r a = 0 \<longleftrightarrow> r = 0"
huffman@44828
   750
  by (simp add: rcis_def)
huffman@44828
   751
huffman@44827
   752
lemma DeMoivre2: "(rcis r a) ^ n = rcis (r ^ n) (real n * a)"
huffman@44827
   753
  by (simp add: rcis_def power_mult_distrib DeMoivre)
huffman@44827
   754
huffman@44827
   755
lemma rcis_inverse: "inverse(rcis r a) = rcis (1/r) (-a)"
huffman@44827
   756
  by (simp add: divide_inverse rcis_def)
huffman@44827
   757
huffman@44827
   758
lemma rcis_divide: "rcis r1 a / rcis r2 b = rcis (r1/r2) (a - b)"
huffman@44828
   759
  by (simp add: rcis_def cis_divide [symmetric])
huffman@44827
   760
wenzelm@60758
   761
subsubsection \<open>Complex exponential\<close>
huffman@44827
   762
hoelzl@56889
   763
lemma cis_conv_exp: "cis b = exp (\<i> * b)"
hoelzl@56889
   764
proof -
hoelzl@56889
   765
  { fix n :: nat
hoelzl@56889
   766
    have "\<i> ^ n = fact n *\<^sub>R (cos_coeff n + \<i> * sin_coeff n)"
hoelzl@56889
   767
      by (induct n)
hoelzl@56889
   768
         (simp_all add: sin_coeff_Suc cos_coeff_Suc complex_eq_iff Re_divide Im_divide field_simps
lp15@61609
   769
                        power2_eq_square of_nat_Suc add_nonneg_eq_0_iff)
hoelzl@56889
   770
    then have "(\<i> * complex_of_real b) ^ n /\<^sub>R fact n =
hoelzl@56889
   771
        of_real (cos_coeff n * b^n) + \<i> * of_real (sin_coeff n * b^n)"
hoelzl@56889
   772
      by (simp add: field_simps) }
lp15@59658
   773
  then show ?thesis using sin_converges [of b] cos_converges [of b]
hoelzl@56889
   774
    by (auto simp add: cis.ctr exp_def simp del: of_real_mult
lp15@59658
   775
             intro!: sums_unique sums_add sums_mult sums_of_real)
huffman@44291
   776
qed
huffman@44291
   777
lp15@61762
   778
lemma exp_eq_polar: "exp z = exp (Re z) * cis (Im z)"
hoelzl@56889
   779
  unfolding cis_conv_exp exp_of_real [symmetric] mult_exp_exp by (cases z) simp
huffman@20557
   780
huffman@44828
   781
lemma Re_exp: "Re (exp z) = exp (Re z) * cos (Im z)"
lp15@61762
   782
  unfolding exp_eq_polar by simp
huffman@44828
   783
huffman@44828
   784
lemma Im_exp: "Im (exp z) = exp (Re z) * sin (Im z)"
lp15@61762
   785
  unfolding exp_eq_polar by simp
huffman@44828
   786
lp15@59746
   787
lemma norm_cos_sin [simp]: "norm (Complex (cos t) (sin t)) = 1"
lp15@59746
   788
  by (simp add: norm_complex_def)
lp15@59746
   789
lp15@59746
   790
lemma norm_exp_eq_Re [simp]: "norm (exp z) = exp (Re z)"
lp15@61762
   791
  by (simp add: cis.code cmod_complex_polar exp_eq_polar)
lp15@59746
   792
lp15@61762
   793
lemma complex_exp_exists: "\<exists>a r. z = complex_of_real r * exp a"
lp15@59746
   794
  apply (insert rcis_Ex [of z])
lp15@61762
   795
  apply (auto simp add: exp_eq_polar rcis_def mult.assoc [symmetric])
lp15@59746
   796
  apply (rule_tac x = "ii * complex_of_real a" in exI, auto)
lp15@59746
   797
  done
paulson@14323
   798
lp15@61848
   799
lemma exp_pi_i [simp]: "exp(of_real pi * ii) = -1"
lp15@61848
   800
  by (metis cis_conv_exp cis_pi mult.commute)
lp15@61848
   801
lp15@61848
   802
lemma exp_two_pi_i [simp]: "exp(2 * of_real pi * ii) = 1"
lp15@61762
   803
  by (simp add: exp_eq_polar complex_eq_iff)
paulson@14387
   804
wenzelm@60758
   805
subsubsection \<open>Complex argument\<close>
huffman@44844
   806
huffman@44844
   807
definition arg :: "complex \<Rightarrow> real" where
huffman@44844
   808
  "arg z = (if z = 0 then 0 else (SOME a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi))"
huffman@44844
   809
huffman@44844
   810
lemma arg_zero: "arg 0 = 0"
huffman@44844
   811
  by (simp add: arg_def)
huffman@44844
   812
huffman@44844
   813
lemma arg_unique:
huffman@44844
   814
  assumes "sgn z = cis x" and "-pi < x" and "x \<le> pi"
huffman@44844
   815
  shows "arg z = x"
huffman@44844
   816
proof -
huffman@44844
   817
  from assms have "z \<noteq> 0" by auto
huffman@44844
   818
  have "(SOME a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi) = x"
huffman@44844
   819
  proof
wenzelm@63040
   820
    fix a
wenzelm@63040
   821
    define d where "d = a - x"
huffman@44844
   822
    assume a: "sgn z = cis a \<and> - pi < a \<and> a \<le> pi"
huffman@44844
   823
    from a assms have "- (2*pi) < d \<and> d < 2*pi"
huffman@44844
   824
      unfolding d_def by simp
huffman@44844
   825
    moreover from a assms have "cos a = cos x" and "sin a = sin x"
huffman@44844
   826
      by (simp_all add: complex_eq_iff)
wenzelm@53374
   827
    hence cos: "cos d = 1" unfolding d_def cos_diff by simp
wenzelm@53374
   828
    moreover from cos have "sin d = 0" by (rule cos_one_sin_zero)
huffman@44844
   829
    ultimately have "d = 0"
haftmann@58709
   830
      unfolding sin_zero_iff
haftmann@58740
   831
      by (auto elim!: evenE dest!: less_2_cases)
huffman@44844
   832
    thus "a = x" unfolding d_def by simp
huffman@44844
   833
  qed (simp add: assms del: Re_sgn Im_sgn)
wenzelm@60758
   834
  with \<open>z \<noteq> 0\<close> show "arg z = x"
huffman@44844
   835
    unfolding arg_def by simp
huffman@44844
   836
qed
huffman@44844
   837
huffman@44844
   838
lemma arg_correct:
huffman@44844
   839
  assumes "z \<noteq> 0" shows "sgn z = cis (arg z) \<and> -pi < arg z \<and> arg z \<le> pi"
huffman@44844
   840
proof (simp add: arg_def assms, rule someI_ex)
huffman@44844
   841
  obtain r a where z: "z = rcis r a" using rcis_Ex by fast
huffman@44844
   842
  with assms have "r \<noteq> 0" by auto
wenzelm@63040
   843
  define b where "b = (if 0 < r then a else a + pi)"
huffman@44844
   844
  have b: "sgn z = cis b"
wenzelm@60758
   845
    unfolding z b_def rcis_def using \<open>r \<noteq> 0\<close>
hoelzl@56889
   846
    by (simp add: of_real_def sgn_scaleR sgn_if complex_eq_iff)
huffman@44844
   847
  have cis_2pi_nat: "\<And>n. cis (2 * pi * real_of_nat n) = 1"
hoelzl@56889
   848
    by (induct_tac n) (simp_all add: distrib_left cis_mult [symmetric] complex_eq_iff)
huffman@44844
   849
  have cis_2pi_int: "\<And>x. cis (2 * pi * real_of_int x) = 1"
hoelzl@56889
   850
    by (case_tac x rule: int_diff_cases)
hoelzl@56889
   851
       (simp add: right_diff_distrib cis_divide [symmetric] cis_2pi_nat)
wenzelm@63040
   852
  define c where "c = b - 2 * pi * of_int \<lceil>(b - pi) / (2 * pi)\<rceil>"
huffman@44844
   853
  have "sgn z = cis c"
huffman@44844
   854
    unfolding b c_def
huffman@44844
   855
    by (simp add: cis_divide [symmetric] cis_2pi_int)
huffman@44844
   856
  moreover have "- pi < c \<and> c \<le> pi"
huffman@44844
   857
    using ceiling_correct [of "(b - pi) / (2*pi)"]
lp15@61649
   858
    by (simp add: c_def less_divide_eq divide_le_eq algebra_simps del: le_of_int_ceiling)
huffman@44844
   859
  ultimately show "\<exists>a. sgn z = cis a \<and> -pi < a \<and> a \<le> pi" by fast
huffman@44844
   860
qed
huffman@44844
   861
huffman@44844
   862
lemma arg_bounded: "- pi < arg z \<and> arg z \<le> pi"
hoelzl@56889
   863
  by (cases "z = 0") (simp_all add: arg_zero arg_correct)
huffman@44844
   864
huffman@44844
   865
lemma cis_arg: "z \<noteq> 0 \<Longrightarrow> cis (arg z) = sgn z"
huffman@44844
   866
  by (simp add: arg_correct)
huffman@44844
   867
huffman@44844
   868
lemma rcis_cmod_arg: "rcis (cmod z) (arg z) = z"
hoelzl@56889
   869
  by (cases "z = 0") (simp_all add: rcis_def cis_arg sgn_div_norm of_real_def)
hoelzl@56889
   870
hoelzl@56889
   871
lemma cos_arg_i_mult_zero [simp]: "y \<noteq> 0 \<Longrightarrow> Re y = 0 \<Longrightarrow> cos (arg y) = 0"
hoelzl@56889
   872
  using cis_arg [of y] by (simp add: complex_eq_iff)
hoelzl@56889
   873
wenzelm@60758
   874
subsection \<open>Square root of complex numbers\<close>
hoelzl@56889
   875
hoelzl@56889
   876
primcorec csqrt :: "complex \<Rightarrow> complex" where
hoelzl@56889
   877
  "Re (csqrt z) = sqrt ((cmod z + Re z) / 2)"
hoelzl@56889
   878
| "Im (csqrt z) = (if Im z = 0 then 1 else sgn (Im z)) * sqrt ((cmod z - Re z) / 2)"
hoelzl@56889
   879
hoelzl@56889
   880
lemma csqrt_of_real_nonneg [simp]: "Im x = 0 \<Longrightarrow> Re x \<ge> 0 \<Longrightarrow> csqrt x = sqrt (Re x)"
hoelzl@56889
   881
  by (simp add: complex_eq_iff norm_complex_def)
hoelzl@56889
   882
hoelzl@56889
   883
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
   884
  by (simp add: complex_eq_iff norm_complex_def)
hoelzl@56889
   885
lp15@59862
   886
lemma of_real_sqrt: "x \<ge> 0 \<Longrightarrow> of_real (sqrt x) = csqrt (of_real x)"
lp15@59862
   887
  by (simp add: complex_eq_iff norm_complex_def)
lp15@59862
   888
hoelzl@56889
   889
lemma csqrt_0 [simp]: "csqrt 0 = 0"
hoelzl@56889
   890
  by simp
hoelzl@56889
   891
hoelzl@56889
   892
lemma csqrt_1 [simp]: "csqrt 1 = 1"
hoelzl@56889
   893
  by simp
hoelzl@56889
   894
hoelzl@56889
   895
lemma csqrt_ii [simp]: "csqrt \<i> = (1 + \<i>) / sqrt 2"
hoelzl@56889
   896
  by (simp add: complex_eq_iff Re_divide Im_divide real_sqrt_divide real_div_sqrt)
huffman@44844
   897
lp15@59741
   898
lemma power2_csqrt[simp,algebra]: "(csqrt z)\<^sup>2 = z"
hoelzl@56889
   899
proof cases
hoelzl@56889
   900
  assume "Im z = 0" then show ?thesis
hoelzl@56889
   901
    using real_sqrt_pow2[of "Re z"] real_sqrt_pow2[of "- Re z"]
hoelzl@56889
   902
    by (cases "0::real" "Re z" rule: linorder_cases)
hoelzl@56889
   903
       (simp_all add: complex_eq_iff Re_power2 Im_power2 power2_eq_square cmod_eq_Re)
hoelzl@56889
   904
next
hoelzl@56889
   905
  assume "Im z \<noteq> 0"
hoelzl@56889
   906
  moreover
hoelzl@56889
   907
  have "cmod z * cmod z - Re z * Re z = Im z * Im z"
hoelzl@56889
   908
    by (simp add: norm_complex_def power2_eq_square)
hoelzl@56889
   909
  moreover
hoelzl@56889
   910
  have "\<bar>Re z\<bar> \<le> cmod z"
hoelzl@56889
   911
    by (simp add: norm_complex_def)
hoelzl@56889
   912
  ultimately show ?thesis
hoelzl@56889
   913
    by (simp add: Re_power2 Im_power2 complex_eq_iff real_sgn_eq
hoelzl@56889
   914
                  field_simps real_sqrt_mult[symmetric] real_sqrt_divide)
hoelzl@56889
   915
qed
hoelzl@56889
   916
hoelzl@56889
   917
lemma csqrt_eq_0 [simp]: "csqrt z = 0 \<longleftrightarrow> z = 0"
hoelzl@56889
   918
  by auto (metis power2_csqrt power_eq_0_iff)
hoelzl@56889
   919
hoelzl@56889
   920
lemma csqrt_eq_1 [simp]: "csqrt z = 1 \<longleftrightarrow> z = 1"
hoelzl@56889
   921
  by auto (metis power2_csqrt power2_eq_1_iff)
hoelzl@56889
   922
hoelzl@56889
   923
lemma csqrt_principal: "0 < Re (csqrt z) \<or> Re (csqrt z) = 0 \<and> 0 \<le> Im (csqrt z)"
hoelzl@56889
   924
  by (auto simp add: not_less cmod_plus_Re_le_0_iff Im_eq_0)
hoelzl@56889
   925
hoelzl@56889
   926
lemma Re_csqrt: "0 \<le> Re (csqrt z)"
hoelzl@56889
   927
  by (metis csqrt_principal le_less)
hoelzl@56889
   928
hoelzl@56889
   929
lemma csqrt_square:
hoelzl@56889
   930
  assumes "0 < Re b \<or> (Re b = 0 \<and> 0 \<le> Im b)"
hoelzl@56889
   931
  shows "csqrt (b^2) = b"
hoelzl@56889
   932
proof -
hoelzl@56889
   933
  have "csqrt (b^2) = b \<or> csqrt (b^2) = - b"
hoelzl@56889
   934
    unfolding power2_eq_iff[symmetric] by (simp add: power2_csqrt)
hoelzl@56889
   935
  moreover have "csqrt (b^2) \<noteq> -b \<or> b = 0"
hoelzl@56889
   936
    using csqrt_principal[of "b ^ 2"] assms by (intro disjCI notI) (auto simp: complex_eq_iff)
hoelzl@56889
   937
  ultimately show ?thesis
hoelzl@56889
   938
    by auto
hoelzl@56889
   939
qed
hoelzl@56889
   940
lp15@59746
   941
lemma csqrt_unique:
lp15@59746
   942
    "w^2 = z \<Longrightarrow> (0 < Re w \<or> Re w = 0 \<and> 0 \<le> Im w) \<Longrightarrow> csqrt z = w"
lp15@59746
   943
  by (auto simp: csqrt_square)
lp15@59746
   944
lp15@59613
   945
lemma csqrt_minus [simp]:
hoelzl@56889
   946
  assumes "Im x < 0 \<or> (Im x = 0 \<and> 0 \<le> Re x)"
hoelzl@56889
   947
  shows "csqrt (- x) = \<i> * csqrt x"
hoelzl@56889
   948
proof -
hoelzl@56889
   949
  have "csqrt ((\<i> * csqrt x)^2) = \<i> * csqrt x"
hoelzl@56889
   950
  proof (rule csqrt_square)
hoelzl@56889
   951
    have "Im (csqrt x) \<le> 0"
hoelzl@56889
   952
      using assms by (auto simp add: cmod_eq_Re mult_le_0_iff field_simps complex_Re_le_cmod)
hoelzl@56889
   953
    then show "0 < Re (\<i> * csqrt x) \<or> Re (\<i> * csqrt x) = 0 \<and> 0 \<le> Im (\<i> * csqrt x)"
hoelzl@56889
   954
      by (auto simp add: Re_csqrt simp del: csqrt.simps)
hoelzl@56889
   955
  qed
hoelzl@56889
   956
  also have "(\<i> * csqrt x)^2 = - x"
lp15@59746
   957
    by (simp add: power_mult_distrib)
hoelzl@56889
   958
  finally show ?thesis .
hoelzl@56889
   959
qed
huffman@44844
   960
wenzelm@60758
   961
text \<open>Legacy theorem names\<close>
huffman@44065
   962
huffman@44065
   963
lemmas expand_complex_eq = complex_eq_iff
huffman@44065
   964
lemmas complex_Re_Im_cancel_iff = complex_eq_iff
huffman@44065
   965
lemmas complex_equality = complex_eqI
hoelzl@56889
   966
lemmas cmod_def = norm_complex_def
hoelzl@56889
   967
lemmas complex_norm_def = norm_complex_def
hoelzl@56889
   968
lemmas complex_divide_def = divide_complex_def
hoelzl@56889
   969
hoelzl@56889
   970
lemma legacy_Complex_simps:
hoelzl@56889
   971
  shows Complex_eq_0: "Complex a b = 0 \<longleftrightarrow> a = 0 \<and> b = 0"
hoelzl@56889
   972
    and complex_add: "Complex a b + Complex c d = Complex (a + c) (b + d)"
hoelzl@56889
   973
    and complex_minus: "- (Complex a b) = Complex (- a) (- b)"
hoelzl@56889
   974
    and complex_diff: "Complex a b - Complex c d = Complex (a - c) (b - d)"
hoelzl@56889
   975
    and Complex_eq_1: "Complex a b = 1 \<longleftrightarrow> a = 1 \<and> b = 0"
hoelzl@56889
   976
    and Complex_eq_neg_1: "Complex a b = - 1 \<longleftrightarrow> a = - 1 \<and> b = 0"
hoelzl@56889
   977
    and complex_mult: "Complex a b * Complex c d = Complex (a * c - b * d) (a * d + b * c)"
hoelzl@56889
   978
    and complex_inverse: "inverse (Complex a b) = Complex (a / (a\<^sup>2 + b\<^sup>2)) (- b / (a\<^sup>2 + b\<^sup>2))"
hoelzl@56889
   979
    and Complex_eq_numeral: "Complex a b = numeral w \<longleftrightarrow> a = numeral w \<and> b = 0"
hoelzl@56889
   980
    and Complex_eq_neg_numeral: "Complex a b = - numeral w \<longleftrightarrow> a = - numeral w \<and> b = 0"
hoelzl@56889
   981
    and complex_scaleR: "scaleR r (Complex a b) = Complex (r * a) (r * b)"
hoelzl@56889
   982
    and Complex_eq_i: "(Complex x y = ii) = (x = 0 \<and> y = 1)"
hoelzl@56889
   983
    and i_mult_Complex: "ii * Complex a b = Complex (- b) a"
hoelzl@56889
   984
    and Complex_mult_i: "Complex a b * ii = Complex (- b) a"
hoelzl@56889
   985
    and i_complex_of_real: "ii * complex_of_real r = Complex 0 r"
hoelzl@56889
   986
    and complex_of_real_i: "complex_of_real r * ii = Complex 0 r"
hoelzl@56889
   987
    and Complex_add_complex_of_real: "Complex x y + complex_of_real r = Complex (x+r) y"
hoelzl@56889
   988
    and complex_of_real_add_Complex: "complex_of_real r + Complex x y = Complex (r+x) y"
hoelzl@56889
   989
    and Complex_mult_complex_of_real: "Complex x y * complex_of_real r = Complex (x*r) (y*r)"
hoelzl@56889
   990
    and complex_of_real_mult_Complex: "complex_of_real r * Complex x y = Complex (r*x) (r*y)"
hoelzl@56889
   991
    and complex_eq_cancel_iff2: "(Complex x y = complex_of_real xa) = (x = xa & y = 0)"
hoelzl@56889
   992
    and complex_cn: "cnj (Complex a b) = Complex a (- b)"
hoelzl@56889
   993
    and Complex_setsum': "setsum (%x. Complex (f x) 0) s = Complex (setsum f s) 0"
hoelzl@56889
   994
    and Complex_setsum: "Complex (setsum f s) 0 = setsum (%x. Complex (f x) 0) s"
hoelzl@56889
   995
    and complex_of_real_def: "complex_of_real r = Complex r 0"
hoelzl@56889
   996
    and complex_norm: "cmod (Complex x y) = sqrt (x\<^sup>2 + y\<^sup>2)"
hoelzl@56889
   997
  by (simp_all add: norm_complex_def field_simps complex_eq_iff Re_divide Im_divide del: Complex_eq)
hoelzl@56889
   998
hoelzl@56889
   999
lemma Complex_in_Reals: "Complex x 0 \<in> \<real>"
hoelzl@56889
  1000
  by (metis Reals_of_real complex_of_real_def)
huffman@44065
  1001
paulson@13957
  1002
end