MPE Home Metamath Proof Explorer < Previous   Next >
Nearby theorems
Mirrors  >  Home  >  MPE Home  >  Th. List  >  cosval Structured version   Visualization version   GIF version

Theorem cosval 14785
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 6618 . . . . 5 (𝑥 = 𝐴 → (i · 𝑥) = (i · 𝐴))
21fveq2d 6157 . . . 4 (𝑥 = 𝐴 → (exp‘(i · 𝑥)) = (exp‘(i · 𝐴)))
3 oveq2 6618 . . . . 5 (𝑥 = 𝐴 → (-i · 𝑥) = (-i · 𝐴))
43fveq2d 6157 . . . 4 (𝑥 = 𝐴 → (exp‘(-i · 𝑥)) = (exp‘(-i · 𝐴)))
52, 4oveq12d 6628 . . 3 (𝑥 = 𝐴 → ((exp‘(i · 𝑥)) + (exp‘(-i · 𝑥))) = ((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))))
65oveq1d 6625 . 2 (𝑥 = 𝐴 → (((exp‘(i · 𝑥)) + (exp‘(-i · 𝑥))) / 2) = (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2))
7 df-cos 14733 . 2 cos = (𝑥 ∈ ℂ ↦ (((exp‘(i · 𝑥)) + (exp‘(-i · 𝑥))) / 2))
8 ovex 6638 . 2 (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2) ∈ V
96, 7, 8fvmpt 6244 1 (𝐴 ∈ ℂ → (cos‘𝐴) = (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2))
Colors of variables: wff setvar class
Syntax hints:  wi 4   = wceq 1480  wcel 1987  cfv 5852  (class class class)co 6610  cc 9885  ici 9889   + caddc 9890   · cmul 9892  -cneg 10218   / cdiv 10635  2c2 11021  expce 14724  cosccos 14727
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1836  ax-6 1885  ax-7 1932  ax-9 1996  ax-10 2016  ax-11 2031  ax-12 2044  ax-13 2245  ax-ext 2601  ax-sep 4746  ax-nul 4754  ax-pr 4872
This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3an 1038  df-tru 1483  df-ex 1702  df-nf 1707  df-sb 1878  df-eu 2473  df-mo 2474  df-clab 2608  df-cleq 2614  df-clel 2617  df-nfc 2750  df-ral 2912  df-rex 2913  df-rab 2916  df-v 3191  df-sbc 3422  df-dif 3562  df-un 3564  df-in 3566  df-ss 3573  df-nul 3897  df-if 4064  df-sn 4154  df-pr 4156  df-op 4160  df-uni 4408  df-br 4619  df-opab 4679  df-mpt 4680  df-id 4994  df-xp 5085  df-rel 5086  df-cnv 5087  df-co 5088  df-dm 5089  df-iota 5815  df-fun 5854  df-fv 5860  df-ov 6613  df-cos 14733
This theorem is referenced by:  tanval2  14795  tanval3  14796  recosval  14798  cosneg  14809  efival  14814  coshval  14817  cosadd  14827  cosper  24151  pige3  24186  cosargd  24271  asinsin  24532  cosasin  24544  cosatan  24561
  Copyright terms: Public domain W3C validator