要拆成两个积分的和,题目中没n,怎么括号里要注n啊。原积分=S(0->pi)x(cosx)^2dx-S(-pi->0)x(cosx)^2dx=S(0->pi)x(cosx)^2dx+S(0->pi)x(cosx)^2dx=S(0->pi)x(cos2x+1)dx=S(0->pi)xcos2xdx+S(0->pi)xdx=1/2 S(0->pi)xdsin2x+pi^2/2=-1/2 S(0->pi)sin2xdx+pi^2/2=pi^2/2.
题目中也没有n啊