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Mirrors > Home > MPE Home > Th. List > cos2t | Structured version Visualization version GIF version |
Description: Double-angle formula for cosine. (Contributed by Paul Chapman, 24-Jan-2008.) |
Ref | Expression |
---|---|
cos2t | ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = ((2 · ((cos‘𝐴)↑2)) − 1)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | coscl 15474 | . . . 4 ⊢ (𝐴 ∈ ℂ → (cos‘𝐴) ∈ ℂ) | |
2 | 1 | sqcld 13502 | . . 3 ⊢ (𝐴 ∈ ℂ → ((cos‘𝐴)↑2) ∈ ℂ) |
3 | ax-1cn 10589 | . . . 4 ⊢ 1 ∈ ℂ | |
4 | subsub3 10912 | . . . 4 ⊢ ((((cos‘𝐴)↑2) ∈ ℂ ∧ 1 ∈ ℂ ∧ ((cos‘𝐴)↑2) ∈ ℂ) → (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2))) = ((((cos‘𝐴)↑2) + ((cos‘𝐴)↑2)) − 1)) | |
5 | 3, 4 | mp3an2 1445 | . . 3 ⊢ ((((cos‘𝐴)↑2) ∈ ℂ ∧ ((cos‘𝐴)↑2) ∈ ℂ) → (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2))) = ((((cos‘𝐴)↑2) + ((cos‘𝐴)↑2)) − 1)) |
6 | 2, 2, 5 | syl2anc 586 | . 2 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2))) = ((((cos‘𝐴)↑2) + ((cos‘𝐴)↑2)) − 1)) |
7 | cosadd 15512 | . . . . 5 ⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ∈ ℂ) → (cos‘(𝐴 + 𝐴)) = (((cos‘𝐴) · (cos‘𝐴)) − ((sin‘𝐴) · (sin‘𝐴)))) | |
8 | 7 | anidms 569 | . . . 4 ⊢ (𝐴 ∈ ℂ → (cos‘(𝐴 + 𝐴)) = (((cos‘𝐴) · (cos‘𝐴)) − ((sin‘𝐴) · (sin‘𝐴)))) |
9 | 2times 11767 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (2 · 𝐴) = (𝐴 + 𝐴)) | |
10 | 9 | fveq2d 6669 | . . . 4 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (cos‘(𝐴 + 𝐴))) |
11 | 1 | sqvald 13501 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((cos‘𝐴)↑2) = ((cos‘𝐴) · (cos‘𝐴))) |
12 | sincl 15473 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (sin‘𝐴) ∈ ℂ) | |
13 | 12 | sqvald 13501 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((sin‘𝐴)↑2) = ((sin‘𝐴) · (sin‘𝐴))) |
14 | 11, 13 | oveq12d 7168 | . . . 4 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) − ((sin‘𝐴)↑2)) = (((cos‘𝐴) · (cos‘𝐴)) − ((sin‘𝐴) · (sin‘𝐴)))) |
15 | 8, 10, 14 | 3eqtr4d 2866 | . . 3 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (((cos‘𝐴)↑2) − ((sin‘𝐴)↑2))) |
16 | 12 | sqcld 13502 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → ((sin‘𝐴)↑2) ∈ ℂ) |
17 | 16, 2 | addcomd 10836 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2)) = (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2))) |
18 | sincossq 15523 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2)) = 1) | |
19 | 17, 18 | eqtr3d 2858 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2)) = 1) |
20 | subadd 10883 | . . . . . 6 ⊢ ((1 ∈ ℂ ∧ ((cos‘𝐴)↑2) ∈ ℂ ∧ ((sin‘𝐴)↑2) ∈ ℂ) → ((1 − ((cos‘𝐴)↑2)) = ((sin‘𝐴)↑2) ↔ (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2)) = 1)) | |
21 | 3, 2, 16, 20 | mp3an2i 1462 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((1 − ((cos‘𝐴)↑2)) = ((sin‘𝐴)↑2) ↔ (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2)) = 1)) |
22 | 19, 21 | mpbird 259 | . . . 4 ⊢ (𝐴 ∈ ℂ → (1 − ((cos‘𝐴)↑2)) = ((sin‘𝐴)↑2)) |
23 | 22 | oveq2d 7166 | . . 3 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2))) = (((cos‘𝐴)↑2) − ((sin‘𝐴)↑2))) |
24 | 15, 23 | eqtr4d 2859 | . 2 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2)))) |
25 | 2 | 2timesd 11874 | . . 3 ⊢ (𝐴 ∈ ℂ → (2 · ((cos‘𝐴)↑2)) = (((cos‘𝐴)↑2) + ((cos‘𝐴)↑2))) |
26 | 25 | oveq1d 7165 | . 2 ⊢ (𝐴 ∈ ℂ → ((2 · ((cos‘𝐴)↑2)) − 1) = ((((cos‘𝐴)↑2) + ((cos‘𝐴)↑2)) − 1)) |
27 | 6, 24, 26 | 3eqtr4d 2866 | 1 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = ((2 · ((cos‘𝐴)↑2)) − 1)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 208 = wceq 1533 ∈ wcel 2110 ‘cfv 6350 (class class class)co 7150 ℂcc 10529 1c1 10532 + caddc 10534 · cmul 10536 − cmin 10864 2c2 11686 ↑cexp 13423 sincsin 15411 cosccos 15412 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1792 ax-4 1806 ax-5 1907 ax-6 1966 ax-7 2011 ax-8 2112 ax-9 2120 ax-10 2141 ax-11 2156 ax-12 2172 ax-ext 2793 ax-rep 5183 ax-sep 5196 ax-nul 5203 ax-pow 5259 ax-pr 5322 ax-un 7455 ax-inf2 9098 ax-cnex 10587 ax-resscn 10588 ax-1cn 10589 ax-icn 10590 ax-addcl 10591 ax-addrcl 10592 ax-mulcl 10593 ax-mulrcl 10594 ax-mulcom 10595 ax-addass 10596 ax-mulass 10597 ax-distr 10598 ax-i2m1 10599 ax-1ne0 10600 ax-1rid 10601 ax-rnegex 10602 ax-rrecex 10603 ax-cnre 10604 ax-pre-lttri 10605 ax-pre-lttrn 10606 ax-pre-ltadd 10607 ax-pre-mulgt0 10608 ax-pre-sup 10609 ax-addf 10610 ax-mulf 10611 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-3or 1084 df-3an 1085 df-tru 1536 df-fal 1546 df-ex 1777 df-nf 1781 df-sb 2066 df-mo 2618 df-eu 2650 df-clab 2800 df-cleq 2814 df-clel 2893 df-nfc 2963 df-ne 3017 df-nel 3124 df-ral 3143 df-rex 3144 df-reu 3145 df-rmo 3146 df-rab 3147 df-v 3497 df-sbc 3773 df-csb 3884 df-dif 3939 df-un 3941 df-in 3943 df-ss 3952 df-pss 3954 df-nul 4292 df-if 4468 df-pw 4541 df-sn 4562 df-pr 4564 df-tp 4566 df-op 4568 df-uni 4833 df-int 4870 df-iun 4914 df-br 5060 df-opab 5122 df-mpt 5140 df-tr 5166 df-id 5455 df-eprel 5460 df-po 5469 df-so 5470 df-fr 5509 df-se 5510 df-we 5511 df-xp 5556 df-rel 5557 df-cnv 5558 df-co 5559 df-dm 5560 df-rn 5561 df-res 5562 df-ima 5563 df-pred 6143 df-ord 6189 df-on 6190 df-lim 6191 df-suc 6192 df-iota 6309 df-fun 6352 df-fn 6353 df-f 6354 df-f1 6355 df-fo 6356 df-f1o 6357 df-fv 6358 df-isom 6359 df-riota 7108 df-ov 7153 df-oprab 7154 df-mpo 7155 df-om 7575 df-1st 7683 df-2nd 7684 df-wrecs 7941 df-recs 8002 df-rdg 8040 df-1o 8096 df-oadd 8100 df-er 8283 df-pm 8403 df-en 8504 df-dom 8505 df-sdom 8506 df-fin 8507 df-sup 8900 df-inf 8901 df-oi 8968 df-card 9362 df-pnf 10671 df-mnf 10672 df-xr 10673 df-ltxr 10674 df-le 10675 df-sub 10866 df-neg 10867 df-div 11292 df-nn 11633 df-2 11694 df-3 11695 df-n0 11892 df-z 11976 df-uz 12238 df-rp 12384 df-ico 12738 df-fz 12887 df-fzo 13028 df-fl 13156 df-seq 13364 df-exp 13424 df-fac 13628 df-bc 13657 df-hash 13685 df-shft 14420 df-cj 14452 df-re 14453 df-im 14454 df-sqrt 14588 df-abs 14589 df-limsup 14822 df-clim 14839 df-rlim 14840 df-sum 15037 df-ef 15415 df-sin 15417 df-cos 15418 |
This theorem is referenced by: cos2tsin 15526 cos2bnd 15535 cospi 25052 cos2pi 25056 tangtx 25085 coskpi 25102 sin2h 34876 cos2h 34877 |
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