用三角函数的积化和差形式变换后再积分：∫sin3xcos2xdx==∫[(sin5x+sinx)/2]dx==0.5∫sin5xdx+0.5∫sinxdx==0.5/5(-con5x)+0.5(-conx)+C==-0.1con5x-0.5conx+C.
