∫x(sinx)^2dx
=(1/2)∫x(1-cos2x)dx
=(1/4)x^2-(1/4)∫xdsin2x
=(1/4)x^2-(1/4)(xsin2x)+(1/4)∫sin2xdx
=(1/4)x^2-(1/4)(xsin2x)+(-1/8)cos2x+C