证明：sin^2x+cos^2x=1

怎么证明2(1-sin x)(1+cos x)=(1-sin x+cos x)^2 证明：sin^2x+cos^2x=1 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^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 证明sin^4x-cos^4x=sin^2x-cos^2x (cos X-1)^2+sin^2X=2-2cos X 证明题(要过程) 1-(sin^6x+cos^6x)=3sin^2xcos^2x 如何证明? 证明成立：[cos(3x)-sin(3x)]/(cosx+sinx)=1-2sin(2x). 一道三角函数证明题sin^4 X+cos^4 X=1-2sin^2 X cos^2 X 证明1-sin^6x-cos^2x/1-sin^4x-cos^4x=3/2 证明1-2sinxcosx/cos^2x-sin^2x=cos^2x-sin^2/1+2sinxcosx 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 2sin(π+x)cos(π-x)=sin2x sin^4+sin^2xcos^2x+cos^2x 证明 =1 怎么证明(1/2)sinx=sin(x/2)cos(x/2)怎么证明(1/2)sinx=sin(x/2)cos(x/2) ....[1-(sin x)^2]^1/2=|cos x| 求证明........[1-(sin x)^2]^1/2=|cos x|求证明..... 【高一数学】三角函数的证明题》》》》》》》证明：(sin^4)x+(sin^2)x(cos^2)x+(cos^2)x=1