∫上限圆周率/2,下限负(圆周率/2)cosxcos2xdx,求定积分
问题描述：
∫上限圆周率/2,下限负(圆周率/2)cosxcos2xdx,求定积分
答
原式=∫(1-2sin²x)dsinx
=(sinx-2sin³x/3) (π/2,-π/2)
=(1-2/3)-(-1+2/3)
=2/3