(sin x*sin 3x)sin^2 x+（cos x*cos 3x)cos^2 x 如何变到1/2[(cos 2x-

化简 1/2cos x-根号3/2sin x 根3sin x+cos x 求导f(x) = cos(3x) * cos(2x) + sin(3x) * sin(2x). 2cos x (sin x -cos x)+1 化简[1-(sin^4x-sin^2cos^2x+cos^4x)/(sin^2)]+3sin^2x 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 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x cos 2x /sin^2 x*cos^2 x不定积分 化简（1)√3sin x+cos x (2）√2(sin x-cos x) （3）√2cos x-√6sin x (sin^2x+cos^2x )(sin^2x-cos^2x)怎么得sin^2x-cos^2x? Sin^x怎么变化成 1-cos(2x) /2 Sin x-sin y=2/3 cos x-cos y=1/2 求cos(x-y)