sin^4 x+cos^4 x=?以(i)cos2x表示.(ii)sin2x表示

sin^4 x+cos^4 x=?以(i)cos2x表示.(ii)sin2x表示 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 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)] 化简sin^4x-sin^2x+cos^2x 化简:sin^4 x-sin^2 x+cos^2 x 化简cos^4x+sin^4x 化简:cos^4(X)-sin^4(X) 化简sin^4x+cos^2x 求证(3-sin^4 x-cos^4 x)/2cos^2 x=1+tan^2 x+sin^2 x 化简(sin^2x-cos^4x+cos^2x-sin^4x)/(sin^2x-cos^6x+cos^2x-sin^6x) 关于sin^2x+cos^2x 的应用式子：cos^6x+sin^6x=（cos^2x+sin^2x)(cos^4x-cos^2xsin^x+sin^4x)=(cos^2x+sin^2x)^2-3sin^2xcos^2x 求这两步算法中的具体思路 ps:cos^2x=cosx的二次方 化简y=sin^4x-cos^4x, cos^4x-sin^4x=cos2x 为什么 y=sin^4x+cos^4x的值域 ∫cos^4x/sin^3x dx=?