sin(x/2)+cos(x/2)=1/2,cos2x=?

怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2x 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x 化简(sin x+cos x-1)(sin x-cos x+1)/sin 2x 已知(1+sin x)/cos x=-1/2,则cos/(sin x-1)=? 求证：tan x/2=sin x/(1+cos x) 求证：1-sin(x)=cos(x)*tan(x/2) y=2cos x (sin x+cos x) 2cos x (sin x -cos x)+1 已知sin(x)+3cos(x)=2,求sin(x)-cos(x)/sin(x)+cos(x)=? sin(x/2)cos(x/2)= y=(sin x + COS x)^2 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)] 求证(3-sin^4 x-cos^4 x)/2cos^2 x=1+tan^2 x+sin^2 x 2sin^2x - 5sin x cos x=3 cos^2x,求X, 已知:tan x=2 求:sin x+cos x/sin x-cos x=? Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y) 求证：(sin x+cos x)(1-tan x)=(2sin x)/(tan2x)