证明sin^4+sin^2cos^2+cos^2=1

证明一个sin&cos的等式证明 1+sin^2(x)+sin^4(x)+sin^6(x)=[1-sin^8(x)]/[cos^2(x)] 证明cosA＋cosB＋cosC=1+4sin(A/2)sin(B/2)sin(C/2)证明：cosA＋cosB＋cosC=1+4sin(A/2)sin(B/2)sin(C/2)尽量详细一点选做cosA+cosB+cosC=1+4sin(A/2)sin(B/2)sin(C/2) cos(180-B-C)+cosB+cosC=1+2sin(A/2)[2sin(B/2)sin(C/2)] cos(180-B-C)+cosB+cosC 证明sin^4+sin^2cos^2+cos^2=1 证明sin^4a-cos^4a=sin^2a-cos^2a 证明题：sin^2阿尔法-cos^2阿尔法=sin^4阿尔法-cos^4阿尔法 证明sin^4x-cos^4x=sin^2x-cos^2x 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 sinA+sinB-sinC=4sin(A/2)sin(B/2)cos(C/2)证明上式 证明：sin(2α+β)/sinα - 2cos(α+β)=sinβ/sinα 证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2证明 sin^2A+sin^2B-sin^2A*sin^2B+cos^2A*cos^2B=1 证明cosα(cosα-cosβ)+sinα(sinα-sinβ)=2sin^2(α-β/2)第二个 证明sin(α+β)cosα-1/2[sin(2α+β)-sinβ]=sinβ 证明:2sinθ+sin2θ=4sinθ×cos^2(θ/2) sin^4+sin^2xcos^2x+cos^2x 证明 =1 证明恒等式4sinθcos²θ/2=2sinθ+sin2θ 证明:sin^4a+cos^4a=1-1/2sin^22a 证明sin^4α－cos^4α=2sinα²－1 证明sinθ+cosθ=根号2sin(θ+π/4) cosγ+sinγ=根号2*sin(γ+π/4) 怎么证明