sin^2x=4-2cos^2x

证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2 sin^2x+cos^2x)(sin^4x-sin^2xcos^2x+cos^4x) =sin^4x-sin^2xcos 求导f(x) = cos(3x) * cos(2x) + sin(3x) * sin(2x). 已知函数f(x)=cos^4 x－2sin x cos x－sin^4 x 化简y=sin^2(x)+2sin(x)cos(x)+3cos^2(x) 用cos x表示sin^4 x -sin^2 x +cos^2 x 化简[1-(sin^4x-sin^2cos^2x+cos^4x)/(sin^2)]+3sin^2x 求函数fx=(sin^4x+cos^4x+sin^2x*cos^2x)/（2-sin2x） MATLAB画图,y=sin(x)*(cos(x)-1)/((2*sin(x.^2)+4*cos(x)).^0.5)-( 已知cos 2x=3/5,求sin^4 x+cos^4 x的值