src/HOL/Complex/Complex.thy
 author wenzelm Fri Mar 28 19:43:54 2008 +0100 (2008-03-28) changeset 26462 dac4e2bce00d parent 26311 81a0fc28b0de child 28944 e27abf0db984 permissions -rw-r--r--
avoid rebinding of existing facts;
```     1 (*  Title:       Complex.thy
```
```     2     ID:      \$Id\$
```
```     3     Author:      Jacques D. Fleuriot
```
```     4     Copyright:   2001 University of Edinburgh
```
```     5     Conversion to Isar and new proofs by Lawrence C Paulson, 2003/4
```
```     6 *)
```
```     7
```
```     8 header {* Complex Numbers: Rectangular and Polar Representations *}
```
```     9
```
```    10 theory Complex
```
```    11 imports "../Real/Real" "../Hyperreal/Transcendental"
```
```    12 begin
```
```    13
```
```    14 datatype complex = Complex real real
```
```    15
```
```    16 primrec
```
```    17   Re :: "complex \<Rightarrow> real"
```
```    18 where
```
```    19   Re: "Re (Complex x y) = x"
```
```    20
```
```    21 primrec
```
```    22   Im :: "complex \<Rightarrow> real"
```
```    23 where
```
```    24   Im: "Im (Complex x y) = y"
```
```    25
```
```    26 lemma complex_surj [simp]: "Complex (Re z) (Im z) = z"
```
```    27   by (induct z) simp
```
```    28
```
```    29 lemma complex_equality [intro?]: "\<lbrakk>Re x = Re y; Im x = Im y\<rbrakk> \<Longrightarrow> x = y"
```
```    30   by (induct x, induct y) simp
```
```    31
```
```    32 lemma expand_complex_eq: "x = y \<longleftrightarrow> Re x = Re y \<and> Im x = Im y"
```
```    33   by (induct x, induct y) simp
```
```    34
```
```    35 lemmas complex_Re_Im_cancel_iff = expand_complex_eq
```
```    36
```
```    37
```
```    38 subsection {* Addition and Subtraction *}
```
```    39
```
```    40 instantiation complex :: ab_group_add
```
```    41 begin
```
```    42
```
```    43 definition
```
```    44   complex_zero_def: "0 = Complex 0 0"
```
```    45
```
```    46 definition
```
```    47   complex_add_def: "x + y = Complex (Re x + Re y) (Im x + Im y)"
```
```    48
```
```    49 definition
```
```    50   complex_minus_def: "- x = Complex (- Re x) (- Im x)"
```
```    51
```
```    52 definition
```
```    53   complex_diff_def: "x - (y\<Colon>complex) = x + - y"
```
```    54
```
```    55 lemma Complex_eq_0 [simp]: "Complex a b = 0 \<longleftrightarrow> a = 0 \<and> b = 0"
```
```    56   by (simp add: complex_zero_def)
```
```    57
```
```    58 lemma complex_Re_zero [simp]: "Re 0 = 0"
```
```    59   by (simp add: complex_zero_def)
```
```    60
```
```    61 lemma complex_Im_zero [simp]: "Im 0 = 0"
```
```    62   by (simp add: complex_zero_def)
```
```    63
```
```    64 lemma complex_add [simp]:
```
```    65   "Complex a b + Complex c d = Complex (a + c) (b + d)"
```
```    66   by (simp add: complex_add_def)
```
```    67
```
```    68 lemma complex_Re_add [simp]: "Re (x + y) = Re x + Re y"
```
```    69   by (simp add: complex_add_def)
```
```    70
```
```    71 lemma complex_Im_add [simp]: "Im (x + y) = Im x + Im y"
```
```    72   by (simp add: complex_add_def)
```
```    73
```
```    74 lemma complex_minus [simp]:
```
```    75   "- (Complex a b) = Complex (- a) (- b)"
```
```    76   by (simp add: complex_minus_def)
```
```    77
```
```    78 lemma complex_Re_minus [simp]: "Re (- x) = - Re x"
```
```    79   by (simp add: complex_minus_def)
```
```    80
```
```    81 lemma complex_Im_minus [simp]: "Im (- x) = - Im x"
```
```    82   by (simp add: complex_minus_def)
```
```    83
```
```    84 lemma complex_diff [simp]:
```
```    85   "Complex a b - Complex c d = Complex (a - c) (b - d)"
```
```    86   by (simp add: complex_diff_def)
```
```    87
```
```    88 lemma complex_Re_diff [simp]: "Re (x - y) = Re x - Re y"
```
```    89   by (simp add: complex_diff_def)
```
```    90
```
```    91 lemma complex_Im_diff [simp]: "Im (x - y) = Im x - Im y"
```
```    92   by (simp add: complex_diff_def)
```
```    93
```
```    94 instance
```
```    95   by intro_classes (simp_all add: complex_add_def complex_diff_def)
```
```    96
```
```    97 end
```
```    98
```
```    99
```
```   100
```
```   101 subsection {* Multiplication and Division *}
```
```   102
```
```   103 instantiation complex :: "{field, division_by_zero}"
```
```   104 begin
```
```   105
```
```   106 definition
```
```   107   complex_one_def: "1 = Complex 1 0"
```
```   108
```
```   109 definition
```
```   110   complex_mult_def: "x * y =
```
```   111     Complex (Re x * Re y - Im x * Im y) (Re x * Im y + Im x * Re y)"
```
```   112
```
```   113 definition
```
```   114   complex_inverse_def: "inverse x =
```
```   115     Complex (Re x / ((Re x)\<twosuperior> + (Im x)\<twosuperior>)) (- Im x / ((Re x)\<twosuperior> + (Im x)\<twosuperior>))"
```
```   116
```
```   117 definition
```
```   118   complex_divide_def: "x / (y\<Colon>complex) = x * inverse y"
```
```   119
```
```   120 lemma Complex_eq_1 [simp]: "(Complex a b = 1) = (a = 1 \<and> b = 0)"
```
```   121   by (simp add: complex_one_def)
```
```   122
```
```   123 lemma complex_Re_one [simp]: "Re 1 = 1"
```
```   124   by (simp add: complex_one_def)
```
```   125
```
```   126 lemma complex_Im_one [simp]: "Im 1 = 0"
```
```   127   by (simp add: complex_one_def)
```
```   128
```
```   129 lemma complex_mult [simp]:
```
```   130   "Complex a b * Complex c d = Complex (a * c - b * d) (a * d + b * c)"
```
```   131   by (simp add: complex_mult_def)
```
```   132
```
```   133 lemma complex_Re_mult [simp]: "Re (x * y) = Re x * Re y - Im x * Im y"
```
```   134   by (simp add: complex_mult_def)
```
```   135
```
```   136 lemma complex_Im_mult [simp]: "Im (x * y) = Re x * Im y + Im x * Re y"
```
```   137   by (simp add: complex_mult_def)
```
```   138
```
```   139 lemma complex_inverse [simp]:
```
```   140   "inverse (Complex a b) = Complex (a / (a\<twosuperior> + b\<twosuperior>)) (- b / (a\<twosuperior> + b\<twosuperior>))"
```
```   141   by (simp add: complex_inverse_def)
```
```   142
```
```   143 lemma complex_Re_inverse:
```
```   144   "Re (inverse x) = Re x / ((Re x)\<twosuperior> + (Im x)\<twosuperior>)"
```
```   145   by (simp add: complex_inverse_def)
```
```   146
```
```   147 lemma complex_Im_inverse:
```
```   148   "Im (inverse x) = - Im x / ((Re x)\<twosuperior> + (Im x)\<twosuperior>)"
```
```   149   by (simp add: complex_inverse_def)
```
```   150
```
```   151 instance
```
```   152   by intro_classes (simp_all add: complex_mult_def
```
```   153   right_distrib left_distrib right_diff_distrib left_diff_distrib
```
```   154   complex_inverse_def complex_divide_def
```
```   155   power2_eq_square add_divide_distrib [symmetric]
```
```   156   expand_complex_eq)
```
```   157
```
```   158 end
```
```   159
```
```   160
```
```   161 subsection {* Exponentiation *}
```
```   162
```
```   163 instantiation complex :: recpower
```
```   164 begin
```
```   165
```
```   166 primrec power_complex where
```
```   167   complexpow_0:     "z ^ 0     = (1\<Colon>complex)"
```
```   168   | complexpow_Suc: "z ^ Suc n = (z\<Colon>complex) * z ^ n"
```
```   169
```
```   170 instance by intro_classes simp_all
```
```   171
```
```   172 end
```
```   173
```
```   174
```
```   175 subsection {* Numerals and Arithmetic *}
```
```   176
```
```   177 instantiation complex :: number_ring
```
```   178 begin
```
```   179
```
```   180 definition number_of_complex where
```
```   181   complex_number_of_def: "number_of w = (of_int w \<Colon> complex)"
```
```   182
```
```   183 instance
```
```   184   by intro_classes (simp only: complex_number_of_def)
```
```   185
```
```   186 end
```
```   187
```
```   188 lemma complex_Re_of_nat [simp]: "Re (of_nat n) = of_nat n"
```
```   189 by (induct n) simp_all
```
```   190
```
```   191 lemma complex_Im_of_nat [simp]: "Im (of_nat n) = 0"
```
```   192 by (induct n) simp_all
```
```   193
```
```   194 lemma complex_Re_of_int [simp]: "Re (of_int z) = of_int z"
```
```   195 by (cases z rule: int_diff_cases) simp
```
```   196
```
```   197 lemma complex_Im_of_int [simp]: "Im (of_int z) = 0"
```
```   198 by (cases z rule: int_diff_cases) simp
```
```   199
```
```   200 lemma complex_Re_number_of [simp]: "Re (number_of v) = number_of v"
```
```   201 unfolding number_of_eq by (rule complex_Re_of_int)
```
```   202
```
```   203 lemma complex_Im_number_of [simp]: "Im (number_of v) = 0"
```
```   204 unfolding number_of_eq by (rule complex_Im_of_int)
```
```   205
```
```   206 lemma Complex_eq_number_of [simp]:
```
```   207   "(Complex a b = number_of w) = (a = number_of w \<and> b = 0)"
```
```   208 by (simp add: expand_complex_eq)
```
```   209
```
```   210
```
```   211 subsection {* Scalar Multiplication *}
```
```   212
```
```   213 instantiation complex :: real_field
```
```   214 begin
```
```   215
```
```   216 definition
```
```   217   complex_scaleR_def: "scaleR r x = Complex (r * Re x) (r * Im x)"
```
```   218
```
```   219 lemma complex_scaleR [simp]:
```
```   220   "scaleR r (Complex a b) = Complex (r * a) (r * b)"
```
```   221   unfolding complex_scaleR_def by simp
```
```   222
```
```   223 lemma complex_Re_scaleR [simp]: "Re (scaleR r x) = r * Re x"
```
```   224   unfolding complex_scaleR_def by simp
```
```   225
```
```   226 lemma complex_Im_scaleR [simp]: "Im (scaleR r x) = r * Im x"
```
```   227   unfolding complex_scaleR_def by simp
```
```   228
```
```   229 instance
```
```   230 proof
```
```   231   fix a b :: real and x y :: complex
```
```   232   show "scaleR a (x + y) = scaleR a x + scaleR a y"
```
```   233     by (simp add: expand_complex_eq right_distrib)
```
```   234   show "scaleR (a + b) x = scaleR a x + scaleR b x"
```
```   235     by (simp add: expand_complex_eq left_distrib)
```
```   236   show "scaleR a (scaleR b x) = scaleR (a * b) x"
```
```   237     by (simp add: expand_complex_eq mult_assoc)
```
```   238   show "scaleR 1 x = x"
```
```   239     by (simp add: expand_complex_eq)
```
```   240   show "scaleR a x * y = scaleR a (x * y)"
```
```   241     by (simp add: expand_complex_eq ring_simps)
```
```   242   show "x * scaleR a y = scaleR a (x * y)"
```
```   243     by (simp add: expand_complex_eq ring_simps)
```
```   244 qed
```
```   245
```
```   246 end
```
```   247
```
```   248
```
```   249 subsection{* Properties of Embedding from Reals *}
```
```   250
```
```   251 abbreviation
```
```   252   complex_of_real :: "real \<Rightarrow> complex" where
```
```   253     "complex_of_real \<equiv> of_real"
```
```   254
```
```   255 lemma complex_of_real_def: "complex_of_real r = Complex r 0"
```
```   256 by (simp add: of_real_def complex_scaleR_def)
```
```   257
```
```   258 lemma Re_complex_of_real [simp]: "Re (complex_of_real z) = z"
```
```   259 by (simp add: complex_of_real_def)
```
```   260
```
```   261 lemma Im_complex_of_real [simp]: "Im (complex_of_real z) = 0"
```
```   262 by (simp add: complex_of_real_def)
```
```   263
```
```   264 lemma Complex_add_complex_of_real [simp]:
```
```   265      "Complex x y + complex_of_real r = Complex (x+r) y"
```
```   266 by (simp add: complex_of_real_def)
```
```   267
```
```   268 lemma complex_of_real_add_Complex [simp]:
```
```   269      "complex_of_real r + Complex x y = Complex (r+x) y"
```
```   270 by (simp add: complex_of_real_def)
```
```   271
```
```   272 lemma Complex_mult_complex_of_real:
```
```   273      "Complex x y * complex_of_real r = Complex (x*r) (y*r)"
```
```   274 by (simp add: complex_of_real_def)
```
```   275
```
```   276 lemma complex_of_real_mult_Complex:
```
```   277      "complex_of_real r * Complex x y = Complex (r*x) (r*y)"
```
```   278 by (simp add: complex_of_real_def)
```
```   279
```
```   280
```
```   281 subsection {* Vector Norm *}
```
```   282
```
```   283 instantiation complex :: real_normed_field
```
```   284 begin
```
```   285
```
```   286 definition
```
```   287   complex_norm_def: "norm z = sqrt ((Re z)\<twosuperior> + (Im z)\<twosuperior>)"
```
```   288
```
```   289 abbreviation
```
```   290   cmod :: "complex \<Rightarrow> real" where
```
```   291   "cmod \<equiv> norm"
```
```   292
```
```   293 definition
```
```   294   complex_sgn_def: "sgn x = x /\<^sub>R cmod x"
```
```   295
```
```   296 lemmas cmod_def = complex_norm_def
```
```   297
```
```   298 lemma complex_norm [simp]: "cmod (Complex x y) = sqrt (x\<twosuperior> + y\<twosuperior>)"
```
```   299   by (simp add: complex_norm_def)
```
```   300
```
```   301 instance
```
```   302 proof
```
```   303   fix r :: real and x y :: complex
```
```   304   show "0 \<le> norm x"
```
```   305     by (induct x) simp
```
```   306   show "(norm x = 0) = (x = 0)"
```
```   307     by (induct x) simp
```
```   308   show "norm (x + y) \<le> norm x + norm y"
```
```   309     by (induct x, induct y)
```
```   310        (simp add: real_sqrt_sum_squares_triangle_ineq)
```
```   311   show "norm (scaleR r x) = \<bar>r\<bar> * norm x"
```
```   312     by (induct x)
```
```   313        (simp add: power_mult_distrib right_distrib [symmetric] real_sqrt_mult)
```
```   314   show "norm (x * y) = norm x * norm y"
```
```   315     by (induct x, induct y)
```
```   316        (simp add: real_sqrt_mult [symmetric] power2_eq_square ring_simps)
```
```   317   show "sgn x = x /\<^sub>R cmod x" by(simp add: complex_sgn_def)
```
```   318 qed
```
```   319
```
```   320 end
```
```   321
```
```   322 lemma cmod_unit_one [simp]: "cmod (Complex (cos a) (sin a)) = 1"
```
```   323 by simp
```
```   324
```
```   325 lemma cmod_complex_polar [simp]:
```
```   326      "cmod (complex_of_real r * Complex (cos a) (sin a)) = abs r"
```
```   327 by (simp add: norm_mult)
```
```   328
```
```   329 lemma complex_Re_le_cmod: "Re x \<le> cmod x"
```
```   330 unfolding complex_norm_def
```
```   331 by (rule real_sqrt_sum_squares_ge1)
```
```   332
```
```   333 lemma complex_mod_minus_le_complex_mod [simp]: "- cmod x \<le> cmod x"
```
```   334 by (rule order_trans [OF _ norm_ge_zero], simp)
```
```   335
```
```   336 lemma complex_mod_triangle_ineq2 [simp]: "cmod(b + a) - cmod b \<le> cmod a"
```
```   337 by (rule ord_le_eq_trans [OF norm_triangle_ineq2], simp)
```
```   338
```
```   339 lemmas real_sum_squared_expand = power2_sum [where 'a=real]
```
```   340
```
```   341 lemma abs_Re_le_cmod: "\<bar>Re x\<bar> \<le> cmod x"
```
```   342 by (cases x) simp
```
```   343
```
```   344 lemma abs_Im_le_cmod: "\<bar>Im x\<bar> \<le> cmod x"
```
```   345 by (cases x) simp
```
```   346
```
```   347 subsection {* Completeness of the Complexes *}
```
```   348
```
```   349 interpretation Re: bounded_linear ["Re"]
```
```   350 apply (unfold_locales, simp, simp)
```
```   351 apply (rule_tac x=1 in exI)
```
```   352 apply (simp add: complex_norm_def)
```
```   353 done
```
```   354
```
```   355 interpretation Im: bounded_linear ["Im"]
```
```   356 apply (unfold_locales, simp, simp)
```
```   357 apply (rule_tac x=1 in exI)
```
```   358 apply (simp add: complex_norm_def)
```
```   359 done
```
```   360
```
```   361 lemma LIMSEQ_Complex:
```
```   362   "\<lbrakk>X ----> a; Y ----> b\<rbrakk> \<Longrightarrow> (\<lambda>n. Complex (X n) (Y n)) ----> Complex a b"
```
```   363 apply (rule LIMSEQ_I)
```
```   364 apply (subgoal_tac "0 < r / sqrt 2")
```
```   365 apply (drule_tac r="r / sqrt 2" in LIMSEQ_D, safe)
```
```   366 apply (drule_tac r="r / sqrt 2" in LIMSEQ_D, safe)
```
```   367 apply (rename_tac M N, rule_tac x="max M N" in exI, safe)
```
```   368 apply (simp add: real_sqrt_sum_squares_less)
```
```   369 apply (simp add: divide_pos_pos)
```
```   370 done
```
```   371
```
```   372 instance complex :: banach
```
```   373 proof
```
```   374   fix X :: "nat \<Rightarrow> complex"
```
```   375   assume X: "Cauchy X"
```
```   376   from Re.Cauchy [OF X] have 1: "(\<lambda>n. Re (X n)) ----> lim (\<lambda>n. Re (X n))"
```
```   377     by (simp add: Cauchy_convergent_iff convergent_LIMSEQ_iff)
```
```   378   from Im.Cauchy [OF X] have 2: "(\<lambda>n. Im (X n)) ----> lim (\<lambda>n. Im (X n))"
```
```   379     by (simp add: Cauchy_convergent_iff convergent_LIMSEQ_iff)
```
```   380   have "X ----> Complex (lim (\<lambda>n. Re (X n))) (lim (\<lambda>n. Im (X n)))"
```
```   381     using LIMSEQ_Complex [OF 1 2] by simp
```
```   382   thus "convergent X"
```
```   383     by (rule convergentI)
```
```   384 qed
```
```   385
```
```   386
```
```   387 subsection {* The Complex Number @{term "\<i>"} *}
```
```   388
```
```   389 definition
```
```   390   "ii" :: complex  ("\<i>") where
```
```   391   i_def: "ii \<equiv> Complex 0 1"
```
```   392
```
```   393 lemma complex_Re_i [simp]: "Re ii = 0"
```
```   394 by (simp add: i_def)
```
```   395
```
```   396 lemma complex_Im_i [simp]: "Im ii = 1"
```
```   397 by (simp add: i_def)
```
```   398
```
```   399 lemma Complex_eq_i [simp]: "(Complex x y = ii) = (x = 0 \<and> y = 1)"
```
```   400 by (simp add: i_def)
```
```   401
```
```   402 lemma complex_i_not_zero [simp]: "ii \<noteq> 0"
```
```   403 by (simp add: expand_complex_eq)
```
```   404
```
```   405 lemma complex_i_not_one [simp]: "ii \<noteq> 1"
```
```   406 by (simp add: expand_complex_eq)
```
```   407
```
```   408 lemma complex_i_not_number_of [simp]: "ii \<noteq> number_of w"
```
```   409 by (simp add: expand_complex_eq)
```
```   410
```
```   411 lemma i_mult_Complex [simp]: "ii * Complex a b = Complex (- b) a"
```
```   412 by (simp add: expand_complex_eq)
```
```   413
```
```   414 lemma Complex_mult_i [simp]: "Complex a b * ii = Complex (- b) a"
```
```   415 by (simp add: expand_complex_eq)
```
```   416
```
```   417 lemma i_complex_of_real [simp]: "ii * complex_of_real r = Complex 0 r"
```
```   418 by (simp add: i_def complex_of_real_def)
```
```   419
```
```   420 lemma complex_of_real_i [simp]: "complex_of_real r * ii = Complex 0 r"
```
```   421 by (simp add: i_def complex_of_real_def)
```
```   422
```
```   423 lemma i_squared [simp]: "ii * ii = -1"
```
```   424 by (simp add: i_def)
```
```   425
```
```   426 lemma power2_i [simp]: "ii\<twosuperior> = -1"
```
```   427 by (simp add: power2_eq_square)
```
```   428
```
```   429 lemma inverse_i [simp]: "inverse ii = - ii"
```
```   430 by (rule inverse_unique, simp)
```
```   431
```
```   432
```
```   433 subsection {* Complex Conjugation *}
```
```   434
```
```   435 definition
```
```   436   cnj :: "complex \<Rightarrow> complex" where
```
```   437   "cnj z = Complex (Re z) (- Im z)"
```
```   438
```
```   439 lemma complex_cnj [simp]: "cnj (Complex a b) = Complex a (- b)"
```
```   440 by (simp add: cnj_def)
```
```   441
```
```   442 lemma complex_Re_cnj [simp]: "Re (cnj x) = Re x"
```
```   443 by (simp add: cnj_def)
```
```   444
```
```   445 lemma complex_Im_cnj [simp]: "Im (cnj x) = - Im x"
```
```   446 by (simp add: cnj_def)
```
```   447
```
```   448 lemma complex_cnj_cancel_iff [simp]: "(cnj x = cnj y) = (x = y)"
```
```   449 by (simp add: expand_complex_eq)
```
```   450
```
```   451 lemma complex_cnj_cnj [simp]: "cnj (cnj z) = z"
```
```   452 by (simp add: cnj_def)
```
```   453
```
```   454 lemma complex_cnj_zero [simp]: "cnj 0 = 0"
```
```   455 by (simp add: expand_complex_eq)
```
```   456
```
```   457 lemma complex_cnj_zero_iff [iff]: "(cnj z = 0) = (z = 0)"
```
```   458 by (simp add: expand_complex_eq)
```
```   459
```
```   460 lemma complex_cnj_add: "cnj (x + y) = cnj x + cnj y"
```
```   461 by (simp add: expand_complex_eq)
```
```   462
```
```   463 lemma complex_cnj_diff: "cnj (x - y) = cnj x - cnj y"
```
```   464 by (simp add: expand_complex_eq)
```
```   465
```
```   466 lemma complex_cnj_minus: "cnj (- x) = - cnj x"
```
```   467 by (simp add: expand_complex_eq)
```
```   468
```
```   469 lemma complex_cnj_one [simp]: "cnj 1 = 1"
```
```   470 by (simp add: expand_complex_eq)
```
```   471
```
```   472 lemma complex_cnj_mult: "cnj (x * y) = cnj x * cnj y"
```
```   473 by (simp add: expand_complex_eq)
```
```   474
```
```   475 lemma complex_cnj_inverse: "cnj (inverse x) = inverse (cnj x)"
```
```   476 by (simp add: complex_inverse_def)
```
```   477
```
```   478 lemma complex_cnj_divide: "cnj (x / y) = cnj x / cnj y"
```
```   479 by (simp add: complex_divide_def complex_cnj_mult complex_cnj_inverse)
```
```   480
```
```   481 lemma complex_cnj_power: "cnj (x ^ n) = cnj x ^ n"
```
```   482 by (induct n, simp_all add: complex_cnj_mult)
```
```   483
```
```   484 lemma complex_cnj_of_nat [simp]: "cnj (of_nat n) = of_nat n"
```
```   485 by (simp add: expand_complex_eq)
```
```   486
```
```   487 lemma complex_cnj_of_int [simp]: "cnj (of_int z) = of_int z"
```
```   488 by (simp add: expand_complex_eq)
```
```   489
```
```   490 lemma complex_cnj_number_of [simp]: "cnj (number_of w) = number_of w"
```
```   491 by (simp add: expand_complex_eq)
```
```   492
```
```   493 lemma complex_cnj_scaleR: "cnj (scaleR r x) = scaleR r (cnj x)"
```
```   494 by (simp add: expand_complex_eq)
```
```   495
```
```   496 lemma complex_mod_cnj [simp]: "cmod (cnj z) = cmod z"
```
```   497 by (simp add: complex_norm_def)
```
```   498
```
```   499 lemma complex_cnj_complex_of_real [simp]: "cnj (of_real x) = of_real x"
```
```   500 by (simp add: expand_complex_eq)
```
```   501
```
```   502 lemma complex_cnj_i [simp]: "cnj ii = - ii"
```
```   503 by (simp add: expand_complex_eq)
```
```   504
```
```   505 lemma complex_add_cnj: "z + cnj z = complex_of_real (2 * Re z)"
```
```   506 by (simp add: expand_complex_eq)
```
```   507
```
```   508 lemma complex_diff_cnj: "z - cnj z = complex_of_real (2 * Im z) * ii"
```
```   509 by (simp add: expand_complex_eq)
```
```   510
```
```   511 lemma complex_mult_cnj: "z * cnj z = complex_of_real ((Re z)\<twosuperior> + (Im z)\<twosuperior>)"
```
```   512 by (simp add: expand_complex_eq power2_eq_square)
```
```   513
```
```   514 lemma complex_mod_mult_cnj: "cmod (z * cnj z) = (cmod z)\<twosuperior>"
```
```   515 by (simp add: norm_mult power2_eq_square)
```
```   516
```
```   517 interpretation cnj: bounded_linear ["cnj"]
```
```   518 apply (unfold_locales)
```
```   519 apply (rule complex_cnj_add)
```
```   520 apply (rule complex_cnj_scaleR)
```
```   521 apply (rule_tac x=1 in exI, simp)
```
```   522 done
```
```   523
```
```   524
```
```   525 subsection{*The Functions @{term sgn} and @{term arg}*}
```
```   526
```
```   527 text {*------------ Argand -------------*}
```
```   528
```
```   529 definition
```
```   530   arg :: "complex => real" where
```
```   531   "arg z = (SOME a. Re(sgn z) = cos a & Im(sgn z) = sin a & -pi < a & a \<le> pi)"
```
```   532
```
```   533 lemma sgn_eq: "sgn z = z / complex_of_real (cmod z)"
```
```   534 by (simp add: complex_sgn_def divide_inverse scaleR_conv_of_real mult_commute)
```
```   535
```
```   536 lemma i_mult_eq: "ii * ii = complex_of_real (-1)"
```
```   537 by (simp add: i_def complex_of_real_def)
```
```   538
```
```   539 lemma i_mult_eq2 [simp]: "ii * ii = -(1::complex)"
```
```   540 by (simp add: i_def complex_one_def)
```
```   541
```
```   542 lemma complex_eq_cancel_iff2 [simp]:
```
```   543      "(Complex x y = complex_of_real xa) = (x = xa & y = 0)"
```
```   544 by (simp add: complex_of_real_def)
```
```   545
```
```   546 lemma Re_sgn [simp]: "Re(sgn z) = Re(z)/cmod z"
```
```   547 by (simp add: complex_sgn_def divide_inverse)
```
```   548
```
```   549 lemma Im_sgn [simp]: "Im(sgn z) = Im(z)/cmod z"
```
```   550 by (simp add: complex_sgn_def divide_inverse)
```
```   551
```
```   552 lemma complex_inverse_complex_split:
```
```   553      "inverse(complex_of_real x + ii * complex_of_real y) =
```
```   554       complex_of_real(x/(x ^ 2 + y ^ 2)) -
```
```   555       ii * complex_of_real(y/(x ^ 2 + y ^ 2))"
```
```   556 by (simp add: complex_of_real_def i_def diff_minus divide_inverse)
```
```   557
```
```   558 (*----------------------------------------------------------------------------*)
```
```   559 (* Many of the theorems below need to be moved elsewhere e.g. Transc. Also *)
```
```   560 (* many of the theorems are not used - so should they be kept?                *)
```
```   561 (*----------------------------------------------------------------------------*)
```
```   562
```
```   563 lemma cos_arg_i_mult_zero_pos:
```
```   564    "0 < y ==> cos (arg(Complex 0 y)) = 0"
```
```   565 apply (simp add: arg_def abs_if)
```
```   566 apply (rule_tac a = "pi/2" in someI2, auto)
```
```   567 apply (rule order_less_trans [of _ 0], auto)
```
```   568 done
```
```   569
```
```   570 lemma cos_arg_i_mult_zero_neg:
```
```   571    "y < 0 ==> cos (arg(Complex 0 y)) = 0"
```
```   572 apply (simp add: arg_def abs_if)
```
```   573 apply (rule_tac a = "- pi/2" in someI2, auto)
```
```   574 apply (rule order_trans [of _ 0], auto)
```
```   575 done
```
```   576
```
```   577 lemma cos_arg_i_mult_zero [simp]:
```
```   578      "y \<noteq> 0 ==> cos (arg(Complex 0 y)) = 0"
```
```   579 by (auto simp add: linorder_neq_iff cos_arg_i_mult_zero_pos cos_arg_i_mult_zero_neg)
```
```   580
```
```   581
```
```   582 subsection{*Finally! Polar Form for Complex Numbers*}
```
```   583
```
```   584 definition
```
```   585
```
```   586   (* abbreviation for (cos a + i sin a) *)
```
```   587   cis :: "real => complex" where
```
```   588   "cis a = Complex (cos a) (sin a)"
```
```   589
```
```   590 definition
```
```   591   (* abbreviation for r*(cos a + i sin a) *)
```
```   592   rcis :: "[real, real] => complex" where
```
```   593   "rcis r a = complex_of_real r * cis a"
```
```   594
```
```   595 definition
```
```   596   (* e ^ (x + iy) *)
```
```   597   expi :: "complex => complex" where
```
```   598   "expi z = complex_of_real(exp (Re z)) * cis (Im z)"
```
```   599
```
```   600 lemma complex_split_polar:
```
```   601      "\<exists>r a. z = complex_of_real r * (Complex (cos a) (sin a))"
```
```   602 apply (induct z)
```
```   603 apply (auto simp add: polar_Ex complex_of_real_mult_Complex)
```
```   604 done
```
```   605
```
```   606 lemma rcis_Ex: "\<exists>r a. z = rcis r a"
```
```   607 apply (induct z)
```
```   608 apply (simp add: rcis_def cis_def polar_Ex complex_of_real_mult_Complex)
```
```   609 done
```
```   610
```
```   611 lemma Re_rcis [simp]: "Re(rcis r a) = r * cos a"
```
```   612 by (simp add: rcis_def cis_def)
```
```   613
```
```   614 lemma Im_rcis [simp]: "Im(rcis r a) = r * sin a"
```
```   615 by (simp add: rcis_def cis_def)
```
```   616
```
```   617 lemma sin_cos_squared_add2_mult: "(r * cos a)\<twosuperior> + (r * sin a)\<twosuperior> = r\<twosuperior>"
```
```   618 proof -
```
```   619   have "(r * cos a)\<twosuperior> + (r * sin a)\<twosuperior> = r\<twosuperior> * ((cos a)\<twosuperior> + (sin a)\<twosuperior>)"
```
```   620     by (simp only: power_mult_distrib right_distrib)
```
```   621   thus ?thesis by simp
```
```   622 qed
```
```   623
```
```   624 lemma complex_mod_rcis [simp]: "cmod(rcis r a) = abs r"
```
```   625 by (simp add: rcis_def cis_def sin_cos_squared_add2_mult)
```
```   626
```
```   627 lemma complex_mod_sqrt_Re_mult_cnj: "cmod z = sqrt (Re (z * cnj z))"
```
```   628 by (simp add: cmod_def power2_eq_square)
```
```   629
```
```   630 lemma complex_In_mult_cnj_zero [simp]: "Im (z * cnj z) = 0"
```
```   631 by simp
```
```   632
```
```   633
```
```   634 (*---------------------------------------------------------------------------*)
```
```   635 (*  (r1 * cis a) * (r2 * cis b) = r1 * r2 * cis (a + b)                      *)
```
```   636 (*---------------------------------------------------------------------------*)
```
```   637
```
```   638 lemma cis_rcis_eq: "cis a = rcis 1 a"
```
```   639 by (simp add: rcis_def)
```
```   640
```
```   641 lemma rcis_mult: "rcis r1 a * rcis r2 b = rcis (r1*r2) (a + b)"
```
```   642 by (simp add: rcis_def cis_def cos_add sin_add right_distrib right_diff_distrib
```
```   643               complex_of_real_def)
```
```   644
```
```   645 lemma cis_mult: "cis a * cis b = cis (a + b)"
```
```   646 by (simp add: cis_rcis_eq rcis_mult)
```
```   647
```
```   648 lemma cis_zero [simp]: "cis 0 = 1"
```
```   649 by (simp add: cis_def complex_one_def)
```
```   650
```
```   651 lemma rcis_zero_mod [simp]: "rcis 0 a = 0"
```
```   652 by (simp add: rcis_def)
```
```   653
```
```   654 lemma rcis_zero_arg [simp]: "rcis r 0 = complex_of_real r"
```
```   655 by (simp add: rcis_def)
```
```   656
```
```   657 lemma complex_of_real_minus_one:
```
```   658    "complex_of_real (-(1::real)) = -(1::complex)"
```
```   659 by (simp add: complex_of_real_def complex_one_def)
```
```   660
```
```   661 lemma complex_i_mult_minus [simp]: "ii * (ii * x) = - x"
```
```   662 by (simp add: mult_assoc [symmetric])
```
```   663
```
```   664
```
```   665 lemma cis_real_of_nat_Suc_mult:
```
```   666    "cis (real (Suc n) * a) = cis a * cis (real n * a)"
```
```   667 by (simp add: cis_def real_of_nat_Suc left_distrib cos_add sin_add right_distrib)
```
```   668
```
```   669 lemma DeMoivre: "(cis a) ^ n = cis (real n * a)"
```
```   670 apply (induct_tac "n")
```
```   671 apply (auto simp add: cis_real_of_nat_Suc_mult)
```
```   672 done
```
```   673
```
```   674 lemma DeMoivre2: "(rcis r a) ^ n = rcis (r ^ n) (real n * a)"
```
```   675 by (simp add: rcis_def power_mult_distrib DeMoivre)
```
```   676
```
```   677 lemma cis_inverse [simp]: "inverse(cis a) = cis (-a)"
```
```   678 by (simp add: cis_def complex_inverse_complex_split diff_minus)
```
```   679
```
```   680 lemma rcis_inverse: "inverse(rcis r a) = rcis (1/r) (-a)"
```
```   681 by (simp add: divide_inverse rcis_def)
```
```   682
```
```   683 lemma cis_divide: "cis a / cis b = cis (a - b)"
```
```   684 by (simp add: complex_divide_def cis_mult real_diff_def)
```
```   685
```
```   686 lemma rcis_divide: "rcis r1 a / rcis r2 b = rcis (r1/r2) (a - b)"
```
```   687 apply (simp add: complex_divide_def)
```
```   688 apply (case_tac "r2=0", simp)
```
```   689 apply (simp add: rcis_inverse rcis_mult real_diff_def)
```
```   690 done
```
```   691
```
```   692 lemma Re_cis [simp]: "Re(cis a) = cos a"
```
```   693 by (simp add: cis_def)
```
```   694
```
```   695 lemma Im_cis [simp]: "Im(cis a) = sin a"
```
```   696 by (simp add: cis_def)
```
```   697
```
```   698 lemma cos_n_Re_cis_pow_n: "cos (real n * a) = Re(cis a ^ n)"
```
```   699 by (auto simp add: DeMoivre)
```
```   700
```
```   701 lemma sin_n_Im_cis_pow_n: "sin (real n * a) = Im(cis a ^ n)"
```
```   702 by (auto simp add: DeMoivre)
```
```   703
```
```   704 lemma expi_add: "expi(a + b) = expi(a) * expi(b)"
```
```   705 by (simp add: expi_def exp_add cis_mult [symmetric] mult_ac)
```
```   706
```
```   707 lemma expi_zero [simp]: "expi (0::complex) = 1"
```
```   708 by (simp add: expi_def)
```
```   709
```
```   710 lemma complex_expi_Ex: "\<exists>a r. z = complex_of_real r * expi a"
```
```   711 apply (insert rcis_Ex [of z])
```
```   712 apply (auto simp add: expi_def rcis_def mult_assoc [symmetric])
```
```   713 apply (rule_tac x = "ii * complex_of_real a" in exI, auto)
```
```   714 done
```
```   715
```
```   716 lemma expi_two_pi_i [simp]: "expi((2::complex) * complex_of_real pi * ii) = 1"
```
```   717 by (simp add: expi_def cis_def)
```
```   718
```
```   719 end
```