证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4

证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 证明成立：[cos(3x)-sin(3x)]/(cosx+sinx)=1-2sin(2x). 1-(sin^6x+cos^6x)=3sin^2xcos^2x 如何证明? 证明1-sin^6x-cos^2x/1-sin^4x-cos^4x=3/2 怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 证明sin^4x-cos^4x=sin^2x-cos^2x 证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y 证明cos(x+y)cos(x-y)= cos^2(x)-sin^2(y) 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)] 证明：sin^2x+cos^2x=1 证明sin x+cos x的最大值等于 根号2 证明 2sin(π+x)cos(π-x)=sin2x 已知sin(x)+3cos(x)=2,求sin(x)-cos(x)/sin(x)+cos(x)=? sin[cos^2(x^3+x)],求导 (cos X-1)^2+sin^2X=2-2cos X 证明题(要过程) 证明等式：[cos(3x)-sin(3x)]/(cosx+sinx)=1-2sin(2x).成立 一道三角函数证明题sin^4 X+cos^4 X=1-2sin^2 X cos^2 X 证明x∈(0,π/2),cos(cosx)>sin(sinx)