Sin(2x+π/2)怎么会等于cos(2x)

sin^2(x)cos^2(x)积分等于多少 cos^2x-sin^2x等于多少? [sin^2(x)-cos^2(x)] 为什么等于-cos2x 证明sin x+cos x的最大值等于 根号2 cos^4(x)-sin^4(x)等于?是cos^2(x)还是cos2x 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x 已知sin(π/2-x)+sin(π-x)/cos(-x)+sin(2π-x)=2009,则tan(x+5π/4)等于? sin(2x+ π/3）乘cos(2x+π/3)等于 cos 2x /sin^2 x*cos^2 x不定积分 2cos x (sin x -cos x)+1 (sin^2x+cos^2x )(sin^2x-cos^2x)怎么得sin^2x-cos^2x? 化简 cos^2(x)*sin^2(x)-sin^2(x)