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 三角函数证明及化简题1.证明sin^6x＋cos^6x＝（sin^2x＋cos^2x)（cos^4x－cos^2xsin 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2 证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y sin^2x+cos^2x)(sin^4x-sin^2xcos^2x+cos^4x) =sin^4x-sin^2xcos 证明(1-2sin x cos x )/(cos^2x-sin^2x)=(1-tan x)/(1+tan x) 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x 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 已知函数f(x)=cos^4 x－2sin x cos x－sin^4 x 证明∫( 0,π／2 ) (f sin x/(f sin x+f cos x) dx=π /4 求证明：sin的4次方x＋cos的4次方x=1-2sin的2次方x乘cos的2次方x