倍角加分步cos^2x=(cos2x+1)/2原因为化为∫1/2*x^2dx+1/4∫x^2dsin2x=1/6x^3+1/4sin2x*x^2-1/2∫xsin2xdx=1/6x^3+1/4sin2x*x^2+1/4xcos2x-1/4∫cos2xdx=1/6x^3+1/4sin2x*x^2+1/4xcos2x+1/8sin2x思路是这样,错没错不晓得
