sin^2 x-cos^2 x=cos

已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x 求导f(x) = cos(3x) * cos(2x) + sin(3x) * sin(2x). 证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y 化简y=sin^2(x)+2sin(x)cos(x)+3cos^2(x) 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4 cos 2x /sin^2 x*cos^2 x不定积分 2cos x (sin x -cos x)+1 sin(x+y)sin(x-y)=k,求cos^2x-cos^2y sin（sin（sin（sin（x）=cos（cos（cos（cos（x）,X等于多少? 求证（cos^2 x-sin^2 x)(cos^4 x+sin^4 x)+1/4 sin 2x sin 4x=cos 2 已知函数y=(sin x+ cos x)(sin x+cos x)+2cos x*cos x ,求它的递减区间 Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y)