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Mirrors > Home > ILE Home > Th. List > cos2t | 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 11747 | . . . 4 ⊢ (𝐴 ∈ ℂ → (cos‘𝐴) ∈ ℂ) | |
2 | 1 | sqcld 10683 | . . 3 ⊢ (𝐴 ∈ ℂ → ((cos‘𝐴)↑2) ∈ ℂ) |
3 | ax-1cn 7934 | . . . 4 ⊢ 1 ∈ ℂ | |
4 | subsub3 8219 | . . . 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 1336 | . . 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 411 | . 2 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2))) = ((((cos‘𝐴)↑2) + ((cos‘𝐴)↑2)) − 1)) |
7 | cosadd 11777 | . . . . 5 ⊢ ((𝐴 ∈ ℂ ∧ 𝐴 ∈ ℂ) → (cos‘(𝐴 + 𝐴)) = (((cos‘𝐴) · (cos‘𝐴)) − ((sin‘𝐴) · (sin‘𝐴)))) | |
8 | 7 | anidms 397 | . . . 4 ⊢ (𝐴 ∈ ℂ → (cos‘(𝐴 + 𝐴)) = (((cos‘𝐴) · (cos‘𝐴)) − ((sin‘𝐴) · (sin‘𝐴)))) |
9 | 2times 9077 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (2 · 𝐴) = (𝐴 + 𝐴)) | |
10 | 9 | fveq2d 5538 | . . . 4 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (cos‘(𝐴 + 𝐴))) |
11 | 1 | sqvald 10682 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((cos‘𝐴)↑2) = ((cos‘𝐴) · (cos‘𝐴))) |
12 | sincl 11746 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (sin‘𝐴) ∈ ℂ) | |
13 | 12 | sqvald 10682 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((sin‘𝐴)↑2) = ((sin‘𝐴) · (sin‘𝐴))) |
14 | 11, 13 | oveq12d 5914 | . . . 4 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) − ((sin‘𝐴)↑2)) = (((cos‘𝐴) · (cos‘𝐴)) − ((sin‘𝐴) · (sin‘𝐴)))) |
15 | 8, 10, 14 | 3eqtr4d 2232 | . . 3 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (((cos‘𝐴)↑2) − ((sin‘𝐴)↑2))) |
16 | 12 | sqcld 10683 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → ((sin‘𝐴)↑2) ∈ ℂ) |
17 | 16, 2 | addcomd 8138 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2)) = (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2))) |
18 | sincossq 11788 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2)) = 1) | |
19 | 17, 18 | eqtr3d 2224 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2)) = 1) |
20 | subadd 8190 | . . . . . . 7 ⊢ ((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, 20 | mp3an1 1335 | . . . . . 6 ⊢ ((((cos‘𝐴)↑2) ∈ ℂ ∧ ((sin‘𝐴)↑2) ∈ ℂ) → ((1 − ((cos‘𝐴)↑2)) = ((sin‘𝐴)↑2) ↔ (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2)) = 1)) |
22 | 2, 16, 21 | syl2anc 411 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((1 − ((cos‘𝐴)↑2)) = ((sin‘𝐴)↑2) ↔ (((cos‘𝐴)↑2) + ((sin‘𝐴)↑2)) = 1)) |
23 | 19, 22 | mpbird 167 | . . . 4 ⊢ (𝐴 ∈ ℂ → (1 − ((cos‘𝐴)↑2)) = ((sin‘𝐴)↑2)) |
24 | 23 | oveq2d 5912 | . . 3 ⊢ (𝐴 ∈ ℂ → (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2))) = (((cos‘𝐴)↑2) − ((sin‘𝐴)↑2))) |
25 | 15, 24 | eqtr4d 2225 | . 2 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (((cos‘𝐴)↑2) − (1 − ((cos‘𝐴)↑2)))) |
26 | 2 | 2timesd 9191 | . . 3 ⊢ (𝐴 ∈ ℂ → (2 · ((cos‘𝐴)↑2)) = (((cos‘𝐴)↑2) + ((cos‘𝐴)↑2))) |
27 | 26 | oveq1d 5911 | . 2 ⊢ (𝐴 ∈ ℂ → ((2 · ((cos‘𝐴)↑2)) − 1) = ((((cos‘𝐴)↑2) + ((cos‘𝐴)↑2)) − 1)) |
28 | 6, 25, 27 | 3eqtr4d 2232 | 1 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = ((2 · ((cos‘𝐴)↑2)) − 1)) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ↔ wb 105 = wceq 1364 ∈ wcel 2160 ‘cfv 5235 (class class class)co 5896 ℂcc 7839 1c1 7842 + caddc 7844 · cmul 7846 − cmin 8158 2c2 9000 ↑cexp 10550 sincsin 11684 cosccos 11685 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 106 ax-ia2 107 ax-ia3 108 ax-in1 615 ax-in2 616 ax-io 710 ax-5 1458 ax-7 1459 ax-gen 1460 ax-ie1 1504 ax-ie2 1505 ax-8 1515 ax-10 1516 ax-11 1517 ax-i12 1518 ax-bndl 1520 ax-4 1521 ax-17 1537 ax-i9 1541 ax-ial 1545 ax-i5r 1546 ax-13 2162 ax-14 2163 ax-ext 2171 ax-coll 4133 ax-sep 4136 ax-nul 4144 ax-pow 4192 ax-pr 4227 ax-un 4451 ax-setind 4554 ax-iinf 4605 ax-cnex 7932 ax-resscn 7933 ax-1cn 7934 ax-1re 7935 ax-icn 7936 ax-addcl 7937 ax-addrcl 7938 ax-mulcl 7939 ax-mulrcl 7940 ax-addcom 7941 ax-mulcom 7942 ax-addass 7943 ax-mulass 7944 ax-distr 7945 ax-i2m1 7946 ax-0lt1 7947 ax-1rid 7948 ax-0id 7949 ax-rnegex 7950 ax-precex 7951 ax-cnre 7952 ax-pre-ltirr 7953 ax-pre-ltwlin 7954 ax-pre-lttrn 7955 ax-pre-apti 7956 ax-pre-ltadd 7957 ax-pre-mulgt0 7958 ax-pre-mulext 7959 ax-arch 7960 ax-caucvg 7961 |
This theorem depends on definitions: df-bi 117 df-dc 836 df-3or 981 df-3an 982 df-tru 1367 df-fal 1370 df-nf 1472 df-sb 1774 df-eu 2041 df-mo 2042 df-clab 2176 df-cleq 2182 df-clel 2185 df-nfc 2321 df-ne 2361 df-nel 2456 df-ral 2473 df-rex 2474 df-reu 2475 df-rmo 2476 df-rab 2477 df-v 2754 df-sbc 2978 df-csb 3073 df-dif 3146 df-un 3148 df-in 3150 df-ss 3157 df-nul 3438 df-if 3550 df-pw 3592 df-sn 3613 df-pr 3614 df-op 3616 df-uni 3825 df-int 3860 df-iun 3903 df-disj 3996 df-br 4019 df-opab 4080 df-mpt 4081 df-tr 4117 df-id 4311 df-po 4314 df-iso 4315 df-iord 4384 df-on 4386 df-ilim 4387 df-suc 4389 df-iom 4608 df-xp 4650 df-rel 4651 df-cnv 4652 df-co 4653 df-dm 4654 df-rn 4655 df-res 4656 df-ima 4657 df-iota 5196 df-fun 5237 df-fn 5238 df-f 5239 df-f1 5240 df-fo 5241 df-f1o 5242 df-fv 5243 df-isom 5244 df-riota 5852 df-ov 5899 df-oprab 5900 df-mpo 5901 df-1st 6165 df-2nd 6166 df-recs 6330 df-irdg 6395 df-frec 6416 df-1o 6441 df-oadd 6445 df-er 6559 df-en 6767 df-dom 6768 df-fin 6769 df-sup 7013 df-pnf 8024 df-mnf 8025 df-xr 8026 df-ltxr 8027 df-le 8028 df-sub 8160 df-neg 8161 df-reap 8562 df-ap 8569 df-div 8660 df-inn 8950 df-2 9008 df-3 9009 df-4 9010 df-n0 9207 df-z 9284 df-uz 9559 df-q 9650 df-rp 9684 df-ico 9924 df-fz 10039 df-fzo 10173 df-seqfrec 10477 df-exp 10551 df-fac 10738 df-bc 10760 df-ihash 10788 df-cj 10883 df-re 10884 df-im 10885 df-rsqrt 11039 df-abs 11040 df-clim 11319 df-sumdc 11394 df-ef 11688 df-sin 11690 df-cos 11691 |
This theorem is referenced by: cos2tsin 11791 cos2bnd 11800 sin0pilem1 14659 cospi 14678 cos2pi 14682 tangtx 14716 coskpi 14726 |
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