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Mirrors > Home > MPE Home > Th. List > recosval | Structured version Visualization version GIF version |
Description: The cosine of a real number in terms of the exponential function. (Contributed by NM, 30-Apr-2005.) |
Ref | Expression |
---|---|
recosval | ⊢ (𝐴 ∈ ℝ → (cos‘𝐴) = (ℜ‘(exp‘(i · 𝐴)))) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ax-icn 11205 | . . . . . . . 8 ⊢ i ∈ ℂ | |
2 | recn 11236 | . . . . . . . 8 ⊢ (𝐴 ∈ ℝ → 𝐴 ∈ ℂ) | |
3 | cjmul 15129 | . . . . . . . 8 ⊢ ((i ∈ ℂ ∧ 𝐴 ∈ ℂ) → (∗‘(i · 𝐴)) = ((∗‘i) · (∗‘𝐴))) | |
4 | 1, 2, 3 | sylancr 585 | . . . . . . 7 ⊢ (𝐴 ∈ ℝ → (∗‘(i · 𝐴)) = ((∗‘i) · (∗‘𝐴))) |
5 | cji 15146 | . . . . . . . . 9 ⊢ (∗‘i) = -i | |
6 | 5 | oveq1i 7436 | . . . . . . . 8 ⊢ ((∗‘i) · (∗‘𝐴)) = (-i · (∗‘𝐴)) |
7 | cjre 15126 | . . . . . . . . 9 ⊢ (𝐴 ∈ ℝ → (∗‘𝐴) = 𝐴) | |
8 | 7 | oveq2d 7442 | . . . . . . . 8 ⊢ (𝐴 ∈ ℝ → (-i · (∗‘𝐴)) = (-i · 𝐴)) |
9 | 6, 8 | eqtrid 2780 | . . . . . . 7 ⊢ (𝐴 ∈ ℝ → ((∗‘i) · (∗‘𝐴)) = (-i · 𝐴)) |
10 | 4, 9 | eqtrd 2768 | . . . . . 6 ⊢ (𝐴 ∈ ℝ → (∗‘(i · 𝐴)) = (-i · 𝐴)) |
11 | 10 | fveq2d 6906 | . . . . 5 ⊢ (𝐴 ∈ ℝ → (exp‘(∗‘(i · 𝐴))) = (exp‘(-i · 𝐴))) |
12 | mulcl 11230 | . . . . . . 7 ⊢ ((i ∈ ℂ ∧ 𝐴 ∈ ℂ) → (i · 𝐴) ∈ ℂ) | |
13 | 1, 2, 12 | sylancr 585 | . . . . . 6 ⊢ (𝐴 ∈ ℝ → (i · 𝐴) ∈ ℂ) |
14 | efcj 16076 | . . . . . 6 ⊢ ((i · 𝐴) ∈ ℂ → (exp‘(∗‘(i · 𝐴))) = (∗‘(exp‘(i · 𝐴)))) | |
15 | 13, 14 | syl 17 | . . . . 5 ⊢ (𝐴 ∈ ℝ → (exp‘(∗‘(i · 𝐴))) = (∗‘(exp‘(i · 𝐴)))) |
16 | 11, 15 | eqtr3d 2770 | . . . 4 ⊢ (𝐴 ∈ ℝ → (exp‘(-i · 𝐴)) = (∗‘(exp‘(i · 𝐴)))) |
17 | 16 | oveq2d 7442 | . . 3 ⊢ (𝐴 ∈ ℝ → ((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) = ((exp‘(i · 𝐴)) + (∗‘(exp‘(i · 𝐴))))) |
18 | 17 | oveq1d 7441 | . 2 ⊢ (𝐴 ∈ ℝ → (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2) = (((exp‘(i · 𝐴)) + (∗‘(exp‘(i · 𝐴)))) / 2)) |
19 | cosval 16107 | . . 3 ⊢ (𝐴 ∈ ℂ → (cos‘𝐴) = (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2)) | |
20 | 2, 19 | syl 17 | . 2 ⊢ (𝐴 ∈ ℝ → (cos‘𝐴) = (((exp‘(i · 𝐴)) + (exp‘(-i · 𝐴))) / 2)) |
21 | efcl 16066 | . . 3 ⊢ ((i · 𝐴) ∈ ℂ → (exp‘(i · 𝐴)) ∈ ℂ) | |
22 | reval 15093 | . . 3 ⊢ ((exp‘(i · 𝐴)) ∈ ℂ → (ℜ‘(exp‘(i · 𝐴))) = (((exp‘(i · 𝐴)) + (∗‘(exp‘(i · 𝐴)))) / 2)) | |
23 | 13, 21, 22 | 3syl 18 | . 2 ⊢ (𝐴 ∈ ℝ → (ℜ‘(exp‘(i · 𝐴))) = (((exp‘(i · 𝐴)) + (∗‘(exp‘(i · 𝐴)))) / 2)) |
24 | 18, 20, 23 | 3eqtr4d 2778 | 1 ⊢ (𝐴 ∈ ℝ → (cos‘𝐴) = (ℜ‘(exp‘(i · 𝐴)))) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 = wceq 1533 ∈ wcel 2098 ‘cfv 6553 (class class class)co 7426 ℂcc 11144 ℝcr 11145 ici 11148 + caddc 11149 · cmul 11151 -cneg 11483 / cdiv 11909 2c2 12305 ∗ccj 15083 ℜcre 15084 expce 16045 cosccos 16048 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1789 ax-4 1803 ax-5 1905 ax-6 1963 ax-7 2003 ax-8 2100 ax-9 2108 ax-10 2129 ax-11 2146 ax-12 2166 ax-ext 2699 ax-rep 5289 ax-sep 5303 ax-nul 5310 ax-pow 5369 ax-pr 5433 ax-un 7746 ax-inf2 9672 ax-cnex 11202 ax-resscn 11203 ax-1cn 11204 ax-icn 11205 ax-addcl 11206 ax-addrcl 11207 ax-mulcl 11208 ax-mulrcl 11209 ax-mulcom 11210 ax-addass 11211 ax-mulass 11212 ax-distr 11213 ax-i2m1 11214 ax-1ne0 11215 ax-1rid 11216 ax-rnegex 11217 ax-rrecex 11218 ax-cnre 11219 ax-pre-lttri 11220 ax-pre-lttrn 11221 ax-pre-ltadd 11222 ax-pre-mulgt0 11223 ax-pre-sup 11224 |
This theorem depends on definitions: df-bi 206 df-an 395 df-or 846 df-3or 1085 df-3an 1086 df-tru 1536 df-fal 1546 df-ex 1774 df-nf 1778 df-sb 2060 df-mo 2529 df-eu 2558 df-clab 2706 df-cleq 2720 df-clel 2806 df-nfc 2881 df-ne 2938 df-nel 3044 df-ral 3059 df-rex 3068 df-rmo 3374 df-reu 3375 df-rab 3431 df-v 3475 df-sbc 3779 df-csb 3895 df-dif 3952 df-un 3954 df-in 3956 df-ss 3966 df-pss 3968 df-nul 4327 df-if 4533 df-pw 4608 df-sn 4633 df-pr 4635 df-op 4639 df-uni 4913 df-int 4954 df-iun 5002 df-br 5153 df-opab 5215 df-mpt 5236 df-tr 5270 df-id 5580 df-eprel 5586 df-po 5594 df-so 5595 df-fr 5637 df-se 5638 df-we 5639 df-xp 5688 df-rel 5689 df-cnv 5690 df-co 5691 df-dm 5692 df-rn 5693 df-res 5694 df-ima 5695 df-pred 6310 df-ord 6377 df-on 6378 df-lim 6379 df-suc 6380 df-iota 6505 df-fun 6555 df-fn 6556 df-f 6557 df-f1 6558 df-fo 6559 df-f1o 6560 df-fv 6561 df-isom 6562 df-riota 7382 df-ov 7429 df-oprab 7430 df-mpo 7431 df-om 7877 df-1st 7999 df-2nd 8000 df-frecs 8293 df-wrecs 8324 df-recs 8398 df-rdg 8437 df-1o 8493 df-er 8731 df-pm 8854 df-en 8971 df-dom 8972 df-sdom 8973 df-fin 8974 df-sup 9473 df-inf 9474 df-oi 9541 df-card 9970 df-pnf 11288 df-mnf 11289 df-xr 11290 df-ltxr 11291 df-le 11292 df-sub 11484 df-neg 11485 df-div 11910 df-nn 12251 df-2 12313 df-3 12314 df-n0 12511 df-z 12597 df-uz 12861 df-rp 13015 df-ico 13370 df-fz 13525 df-fzo 13668 df-fl 13797 df-seq 14007 df-exp 14067 df-fac 14273 df-hash 14330 df-shft 15054 df-cj 15086 df-re 15087 df-im 15088 df-sqrt 15222 df-abs 15223 df-limsup 15455 df-clim 15472 df-rlim 15473 df-sum 15673 df-ef 16051 df-cos 16054 |
This theorem is referenced by: recos4p 16123 recoscl 16125 cos0 16134 argregt0 26564 argrege0 26565 lawcos 26768 |
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