sin^2x=4-2cos^2x请问下怎么算

sin^2x=4-2cos^2x请问下怎么算 sin^3 x -cos^3 x sin^3 x -cos^3 x =(sin x -cos x )(sin^2 x +sin x*cos x +cos^2 x )问下这个是个公式还是什么?怎么样算出来的? 请问cos^2x/sin^4x的不定积分是多少 证明sin^4x-cos^4x=sin^2x-cos^2x 求证sin^4x-cos^4x=sin^2x-cos^2x 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 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 已知tanx=根号下2 求：1）（sin x+cos x）/（cos x -sin x）的值.2）2sin^2 x-sin x cos x+cos^2 x 的值 y=2cos x (sin x+cos x) 已知sin(x)+3cos(x)=2,求sin(x)-cos(x)/sin(x)+cos(x)=? 化简sin^4x-sin^2x+cos^2x 化简:sin^4 x-sin^2 x+cos^2 x sin(x/2)cos(x/2)= 化简sin^4x+cos^2x y=(sin x + COS x)^2 化简(sin^2x-cos^4x+cos^2x-sin^4x)/(sin^2x-cos^6x+cos^2x-sin^6x) cos 2x +根号下3乘sin 2x