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Mirrors > Home > MPE Home > Th. List > cos2tsin | Structured version Visualization version 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 15831 | . 2 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = ((2 · ((cos‘𝐴)↑2)) − 1)) | |
2 | 2cn 11994 | . . . . . . 7 ⊢ 2 ∈ ℂ | |
3 | sincl 15779 | . . . . . . . 8 ⊢ (𝐴 ∈ ℂ → (sin‘𝐴) ∈ ℂ) | |
4 | 3 | sqcld 13806 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → ((sin‘𝐴)↑2) ∈ ℂ) |
5 | coscl 15780 | . . . . . . . 8 ⊢ (𝐴 ∈ ℂ → (cos‘𝐴) ∈ ℂ) | |
6 | 5 | sqcld 13806 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → ((cos‘𝐴)↑2) ∈ ℂ) |
7 | adddi 10907 | . . . . . . 7 ⊢ ((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 | 2, 4, 6, 7 | mp3an2i 1464 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (2 · (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2))) = ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2)))) |
9 | sincossq 15829 | . . . . . . 7 ⊢ (𝐴 ∈ ℂ → (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2)) = 1) | |
10 | 9 | oveq2d 7276 | . . . . . 6 ⊢ (𝐴 ∈ ℂ → (2 · (((sin‘𝐴)↑2) + ((cos‘𝐴)↑2))) = (2 · 1)) |
11 | 8, 10 | eqtr3d 2779 | . . . . 5 ⊢ (𝐴 ∈ ℂ → ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = (2 · 1)) |
12 | 2t1e2 12082 | . . . . 5 ⊢ (2 · 1) = 2 | |
13 | 11, 12 | eqtrdi 2793 | . . . 4 ⊢ (𝐴 ∈ ℂ → ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = 2) |
14 | mulcl 10902 | . . . . . 6 ⊢ ((2 ∈ ℂ ∧ ((sin‘𝐴)↑2) ∈ ℂ) → (2 · ((sin‘𝐴)↑2)) ∈ ℂ) | |
15 | 2, 4, 14 | sylancr 586 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (2 · ((sin‘𝐴)↑2)) ∈ ℂ) |
16 | mulcl 10902 | . . . . . 6 ⊢ ((2 ∈ ℂ ∧ ((cos‘𝐴)↑2) ∈ ℂ) → (2 · ((cos‘𝐴)↑2)) ∈ ℂ) | |
17 | 2, 6, 16 | sylancr 586 | . . . . 5 ⊢ (𝐴 ∈ ℂ → (2 · ((cos‘𝐴)↑2)) ∈ ℂ) |
18 | subadd 11170 | . . . . 5 ⊢ ((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)) | |
19 | 2, 15, 17, 18 | mp3an2i 1464 | . . . 4 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) = (2 · ((cos‘𝐴)↑2)) ↔ ((2 · ((sin‘𝐴)↑2)) + (2 · ((cos‘𝐴)↑2))) = 2)) |
20 | 13, 19 | mpbird 256 | . . 3 ⊢ (𝐴 ∈ ℂ → (2 − (2 · ((sin‘𝐴)↑2))) = (2 · ((cos‘𝐴)↑2))) |
21 | 20 | oveq1d 7275 | . 2 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 · ((cos‘𝐴)↑2)) − 1)) |
22 | ax-1cn 10876 | . . . . 5 ⊢ 1 ∈ ℂ | |
23 | sub32 11201 | . . . . 5 ⊢ ((2 ∈ ℂ ∧ (2 · ((sin‘𝐴)↑2)) ∈ ℂ ∧ 1 ∈ ℂ) → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 − 1) − (2 · ((sin‘𝐴)↑2)))) | |
24 | 2, 22, 23 | mp3an13 1450 | . . . 4 ⊢ ((2 · ((sin‘𝐴)↑2)) ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 − 1) − (2 · ((sin‘𝐴)↑2)))) |
25 | 15, 24 | syl 17 | . . 3 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = ((2 − 1) − (2 · ((sin‘𝐴)↑2)))) |
26 | 2m1e1 12045 | . . . 4 ⊢ (2 − 1) = 1 | |
27 | 26 | oveq1i 7270 | . . 3 ⊢ ((2 − 1) − (2 · ((sin‘𝐴)↑2))) = (1 − (2 · ((sin‘𝐴)↑2))) |
28 | 25, 27 | eqtrdi 2793 | . 2 ⊢ (𝐴 ∈ ℂ → ((2 − (2 · ((sin‘𝐴)↑2))) − 1) = (1 − (2 · ((sin‘𝐴)↑2)))) |
29 | 1, 21, 28 | 3eqtr2d 2783 | 1 ⊢ (𝐴 ∈ ℂ → (cos‘(2 · 𝐴)) = (1 − (2 · ((sin‘𝐴)↑2)))) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 205 = wceq 1539 ∈ wcel 2107 ‘cfv 6423 (class class class)co 7260 ℂcc 10816 1c1 10819 + caddc 10821 · cmul 10823 − cmin 11151 2c2 11974 ↑cexp 13726 sincsin 15717 cosccos 15718 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1799 ax-4 1813 ax-5 1914 ax-6 1972 ax-7 2012 ax-8 2109 ax-9 2117 ax-10 2138 ax-11 2155 ax-12 2172 ax-ext 2708 ax-rep 5210 ax-sep 5223 ax-nul 5230 ax-pow 5288 ax-pr 5352 ax-un 7571 ax-inf2 9345 ax-cnex 10874 ax-resscn 10875 ax-1cn 10876 ax-icn 10877 ax-addcl 10878 ax-addrcl 10879 ax-mulcl 10880 ax-mulrcl 10881 ax-mulcom 10882 ax-addass 10883 ax-mulass 10884 ax-distr 10885 ax-i2m1 10886 ax-1ne0 10887 ax-1rid 10888 ax-rnegex 10889 ax-rrecex 10890 ax-cnre 10891 ax-pre-lttri 10892 ax-pre-lttrn 10893 ax-pre-ltadd 10894 ax-pre-mulgt0 10895 ax-pre-sup 10896 |
This theorem depends on definitions: df-bi 206 df-an 396 df-or 844 df-3or 1086 df-3an 1087 df-tru 1542 df-fal 1552 df-ex 1784 df-nf 1788 df-sb 2069 df-mo 2539 df-eu 2568 df-clab 2715 df-cleq 2729 df-clel 2815 df-nfc 2887 df-ne 2942 df-nel 3048 df-ral 3067 df-rex 3068 df-reu 3069 df-rmo 3070 df-rab 3071 df-v 3429 df-sbc 3717 df-csb 3834 df-dif 3891 df-un 3893 df-in 3895 df-ss 3905 df-pss 3907 df-nul 4259 df-if 4462 df-pw 4537 df-sn 4564 df-pr 4566 df-tp 4568 df-op 4570 df-uni 4842 df-int 4882 df-iun 4928 df-br 5076 df-opab 5138 df-mpt 5159 df-tr 5193 df-id 5485 df-eprel 5491 df-po 5499 df-so 5500 df-fr 5540 df-se 5541 df-we 5542 df-xp 5591 df-rel 5592 df-cnv 5593 df-co 5594 df-dm 5595 df-rn 5596 df-res 5597 df-ima 5598 df-pred 6196 df-ord 6259 df-on 6260 df-lim 6261 df-suc 6262 df-iota 6381 df-fun 6425 df-fn 6426 df-f 6427 df-f1 6428 df-fo 6429 df-f1o 6430 df-fv 6431 df-isom 6432 df-riota 7217 df-ov 7263 df-oprab 7264 df-mpo 7265 df-om 7693 df-1st 7809 df-2nd 7810 df-frecs 8073 df-wrecs 8104 df-recs 8178 df-rdg 8217 df-1o 8272 df-er 8461 df-pm 8581 df-en 8697 df-dom 8698 df-sdom 8699 df-fin 8700 df-sup 9147 df-inf 9148 df-oi 9215 df-card 9644 df-pnf 10958 df-mnf 10959 df-xr 10960 df-ltxr 10961 df-le 10962 df-sub 11153 df-neg 11154 df-div 11579 df-nn 11920 df-2 11982 df-3 11983 df-n0 12180 df-z 12266 df-uz 12528 df-rp 12676 df-ico 13030 df-fz 13185 df-fzo 13328 df-fl 13456 df-seq 13666 df-exp 13727 df-fac 13932 df-bc 13961 df-hash 13989 df-shft 14722 df-cj 14754 df-re 14755 df-im 14756 df-sqrt 14890 df-abs 14891 df-limsup 15124 df-clim 15141 df-rlim 15142 df-sum 15342 df-ef 15721 df-sin 15723 df-cos 15724 |
This theorem is referenced by: coseq1 25624 |
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