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Theorem cosval 16012
Description: Value of the cosine function. (Contributed by NM, 14-Mar-2005.) (Revised by Mario Carneiro, 10-Nov-2013.)
Assertion
Ref Expression
cosval (𝐴 ∈ ℂ → (cos‘𝐴) = (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2))

Proof of Theorem cosval
Dummy variable 𝑥 is distinct from all other variables.
StepHypRef Expression
1 oveq2 7370 . . . . 5 (𝑥 = 𝐴 → (i · 𝑥) = (i · 𝐴))
21fveq2d 6851 . . . 4 (𝑥 = 𝐴 → (exp‘(i · 𝑥)) = (exp‘(i · 𝐴)))
3 oveq2 7370 . . . . 5 (𝑥 = 𝐴 → (-i · 𝑥) = (-i · 𝐴))
43fveq2d 6851 . . . 4 (𝑥 = 𝐴 → (exp‘(-i · 𝑥)) = (exp‘(-i · 𝐴)))
52, 4oveq12d 7380 . . 3 (𝑥 = 𝐴 → ((exp‘(i · 𝑥)) + (exp‘(-i · 𝑥))) = ((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))))
65oveq1d 7377 . 2 (𝑥 = 𝐴 → (((exp‘(i · 𝑥)) + (exp‘(-i · 𝑥))) / 2) = (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2))
7 df-cos 15960 . 2 cos = (𝑥 ∈ ℂ ↦ (((exp‘(i · 𝑥)) + (exp‘(-i · 𝑥))) / 2))
8 ovex 7395 . 2 (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2) ∈ V
96, 7, 8fvmpt 6953 1 (𝐴 ∈ ℂ → (cos‘𝐴) = (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2))
Colors of variables: wff setvar class
Syntax hints:  wi 4   = wceq 1542  wcel 2107  cfv 6501  (class class class)co 7362  cc 11056  ici 11060   + caddc 11061   · cmul 11063  -cneg 11393   / cdiv 11819  2c2 12215  expce 15951  cosccos 15954
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-10 2138  ax-11 2155  ax-12 2172  ax-ext 2708  ax-sep 5261  ax-nul 5268  ax-pr 5389
This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-3an 1090  df-tru 1545  df-fal 1555  df-ex 1783  df-nf 1787  df-sb 2069  df-mo 2539  df-eu 2568  df-clab 2715  df-cleq 2729  df-clel 2815  df-nfc 2890  df-ne 2945  df-ral 3066  df-rex 3075  df-rab 3411  df-v 3450  df-dif 3918  df-un 3920  df-in 3922  df-ss 3932  df-nul 4288  df-if 4492  df-sn 4592  df-pr 4594  df-op 4598  df-uni 4871  df-br 5111  df-opab 5173  df-mpt 5194  df-id 5536  df-xp 5644  df-rel 5645  df-cnv 5646  df-co 5647  df-dm 5648  df-iota 6453  df-fun 6503  df-fv 6509  df-ov 7365  df-cos 15960
This theorem is referenced by:  tanval2  16022  tanval3  16023  recosval  16025  cosneg  16036  efival  16041  coshval  16044  cosadd  16054  cosper  25855  pige3ALT  25892  cosargd  25979  asinsin  26258  cosasin  26270  cosatan  26287
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