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Mirrors > Home > ILE Home > Th. List > cos2tsin | GIF version |
Description: Double-angle formula for cosine in terms of sine. (Contributed by NM, 12-Sep-2008.) |
Ref | Expression |
---|---|
cos2tsin | ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (1 − (2 · ((sin‘𝐴)↑2)))) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cos2t 11651 | . 2 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = ((2 · ((cos‘𝐴)↑2)) − 1)) | |
2 | sincl 11607 | . . . . . . . 8 ⊢ (𝐴 ∈ ℂ → (sin‘𝐴) ∈ ℂ) | |
3 | 2 | sqcld 10553 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → ((sin‘𝐴)↑2) ∈ ℂ) |
4 | coscl 11608 | . . . . . . . 8 ⊢ (𝐴 ∈ ℂ → (cos‘𝐴) ∈ ℂ) | |
5 | 4 | sqcld 10553 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → ((cos‘𝐴)↑2) ∈ ℂ) |
6 | 2cn 8905 | . . . . . . . 8 ⊢ 2 ∈ ℂ | |
7 | adddi 7865 | . . . . . . . 8 ⊢ ((2 ∈ ℂ ∧ ((sin‘𝐴)↑2) ∈ ℂ ∧ ((cos‘𝐴)↑2) ∈ ℂ) → (2 · (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2))) = ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2)))) | |
8 | 6, 7 | mp3an1 1306 | . . . . . . 7 ⊢ ((((sin‘𝐴)↑2) ∈ ℂ ∧ ((cos‘𝐴)↑2) ∈ ℂ) → (2 · (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2))) = ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2)))) |
9 | 3, 5, 8 | syl2anc 409 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (2 · (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2))) = ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2)))) |
10 | sincossq 11649 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2)) = 1) | |
11 | 10 | oveq2d 5841 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (2 · (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2))) = (2 · 1)) |
12 | 9, 11 | eqtr3d 2192 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = (2 · 1)) |
13 | 2t1e2 8987 | . . . . 5 ⊢ (2 · 1) = 2 | |
14 | 12, 13 | eqtrdi 2206 | . . . 4 ⊢ (𝐴 ∈ ℂ → ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = 2) |
15 | mulcl 7860 | . . . . . 6 ⊢ ((2 ∈ ℂ ∧ ((sin‘𝐴)↑2) ∈ ℂ) → (2 · ((sin‘𝐴)↑2)) ∈ ℂ) | |
16 | 6, 3, 15 | sylancr 411 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (2 · ((sin‘𝐴)↑2)) ∈ ℂ) |
17 | mulcl 7860 | . . . . . 6 ⊢ ((2 ∈ ℂ ∧ ((cos‘𝐴)↑2) ∈ ℂ) → (2 · ((cos‘𝐴)↑2)) ∈ ℂ) | |
18 | 6, 5, 17 | sylancr 411 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (2 · ((cos‘𝐴)↑2)) ∈ ℂ) |
19 | subadd 8079 | . . . . . 6 ⊢ ((2 ∈ ℂ ∧ (2 · ((sin‘𝐴)↑2)) ∈ ℂ ∧ (2 · ((cos‘𝐴)↑2)) ∈ ℂ) → ((2 − (2 · ((sin‘𝐴)↑2))) = (2 · ((cos‘𝐴)↑2)) ↔ ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = 2)) | |
20 | 6, 19 | mp3an1 1306 | . . . . 5 ⊢ (((2 · ((sin‘𝐴)↑2)) ∈ ℂ ∧ (2 · ((cos‘𝐴)↑2)) ∈ ℂ) → ((2 − (2 · ((sin‘𝐴)↑2))) = (2 · ((cos‘𝐴)↑2)) ↔ ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = 2)) |
21 | 16, 18, 20 | syl2anc 409 | . . . 4 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) = (2 · ((cos‘𝐴)↑2)) ↔ ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = 2)) |
22 | 14, 21 | mpbird 166 | . . 3 ⊢ (𝐴 ∈ ℂ → (2 − (2 · ((sin‘𝐴)↑2))) = (2 · ((cos‘𝐴)↑2))) |
23 | 22 | oveq1d 5840 | . 2 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 · ((cos‘𝐴)↑2)) − 1)) |
24 | ax-1cn 7826 | . . . . 5 ⊢ 1 ∈ ℂ | |
25 | sub32 8110 | . . . . 5 ⊢ ((2 ∈ ℂ ∧ (2 · ((sin‘𝐴)↑2)) ∈ ℂ ∧ 1 ∈ ℂ) → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 − 1) − (2 · ((sin‘𝐴)↑2)))) | |
26 | 6, 24, 25 | mp3an13 1310 | . . . 4 ⊢ ((2 · ((sin‘𝐴)↑2)) ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 − 1) − (2 · ((sin‘𝐴)↑2)))) |
27 | 16, 26 | syl 14 | . . 3 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 − 1) − (2 · ((sin‘𝐴)↑2)))) |
28 | 2m1e1 8952 | . . . 4 ⊢ (2 − 1) = 1 | |
29 | 28 | oveq1i 5835 | . . 3 ⊢ ((2 − 1) − (2 · ((sin‘𝐴)↑2))) = (1 − (2 · ((sin‘𝐴)↑2))) |
30 | 27, 29 | eqtrdi 2206 | . 2 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = (1 − (2 · ((sin‘𝐴)↑2)))) |
31 | 1, 23, 30 | 3eqtr2d 2196 | 1 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (1 − (2 · ((sin‘𝐴)↑2)))) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ↔ wb 104 = wceq 1335 ∈ wcel 2128 ‘cfv 5171 (class class class)co 5825 ℂcc 7731 1c1 7734 + caddc 7736 · cmul 7738 − cmin 8047 2c2 8885 ↑cexp 10422 sincsin 11545 cosccos 11546 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 604 ax-in2 605 ax-io 699 ax-5 1427 ax-7 1428 ax-gen 1429 ax-ie1 1473 ax-ie2 1474 ax-8 1484 ax-10 1485 ax-11 1486 ax-i12 1487 ax-bndl 1489 ax-4 1490 ax-17 1506 ax-i9 1510 ax-ial 1514 ax-i5r 1515 ax-13 2130 ax-14 2131 ax-ext 2139 ax-coll 4080 ax-sep 4083 ax-nul 4091 ax-pow 4136 ax-pr 4170 ax-un 4394 ax-setind 4497 ax-iinf 4548 ax-cnex 7824 ax-resscn 7825 ax-1cn 7826 ax-1re 7827 ax-icn 7828 ax-addcl 7829 ax-addrcl 7830 ax-mulcl 7831 ax-mulrcl 7832 ax-addcom 7833 ax-mulcom 7834 ax-addass 7835 ax-mulass 7836 ax-distr 7837 ax-i2m1 7838 ax-0lt1 7839 ax-1rid 7840 ax-0id 7841 ax-rnegex 7842 ax-precex 7843 ax-cnre 7844 ax-pre-ltirr 7845 ax-pre-ltwlin 7846 ax-pre-lttrn 7847 ax-pre-apti 7848 ax-pre-ltadd 7849 ax-pre-mulgt0 7850 ax-pre-mulext 7851 ax-arch 7852 ax-caucvg 7853 |
This theorem depends on definitions: df-bi 116 df-dc 821 df-3or 964 df-3an 965 df-tru 1338 df-fal 1341 df-nf 1441 df-sb 1743 df-eu 2009 df-mo 2010 df-clab 2144 df-cleq 2150 df-clel 2153 df-nfc 2288 df-ne 2328 df-nel 2423 df-ral 2440 df-rex 2441 df-reu 2442 df-rmo 2443 df-rab 2444 df-v 2714 df-sbc 2938 df-csb 3032 df-dif 3104 df-un 3106 df-in 3108 df-ss 3115 df-nul 3395 df-if 3506 df-pw 3545 df-sn 3566 df-pr 3567 df-op 3569 df-uni 3774 df-int 3809 df-iun 3852 df-disj 3944 df-br 3967 df-opab 4027 df-mpt 4028 df-tr 4064 df-id 4254 df-po 4257 df-iso 4258 df-iord 4327 df-on 4329 df-ilim 4330 df-suc 4332 df-iom 4551 df-xp 4593 df-rel 4594 df-cnv 4595 df-co 4596 df-dm 4597 df-rn 4598 df-res 4599 df-ima 4600 df-iota 5136 df-fun 5173 df-fn 5174 df-f 5175 df-f1 5176 df-fo 5177 df-f1o 5178 df-fv 5179 df-isom 5180 df-riota 5781 df-ov 5828 df-oprab 5829 df-mpo 5830 df-1st 6089 df-2nd 6090 df-recs 6253 df-irdg 6318 df-frec 6339 df-1o 6364 df-oadd 6368 df-er 6481 df-en 6687 df-dom 6688 df-fin 6689 df-sup 6929 df-pnf 7915 df-mnf 7916 df-xr 7917 df-ltxr 7918 df-le 7919 df-sub 8049 df-neg 8050 df-reap 8451 df-ap 8458 df-div 8547 df-inn 8835 df-2 8893 df-3 8894 df-4 8895 df-n0 9092 df-z 9169 df-uz 9441 df-q 9530 df-rp 9562 df-ico 9799 df-fz 9914 df-fzo 10046 df-seqfrec 10349 df-exp 10423 df-fac 10604 df-bc 10626 df-ihash 10654 df-cj 10746 df-re 10747 df-im 10748 df-rsqrt 10902 df-abs 10903 df-clim 11180 df-sumdc 11255 df-ef 11549 df-sin 11551 df-cos 11552 |
This theorem is referenced by: (None) |
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