∫(π/2,0)xsinxdx=∫(π/2,0) x d (－cosx) = －xcosx(代入积分限后，为0) + ∫(π/2,0) cosx dx =1
∫[0→π/2] xsinx dx= ∫[π/2→0] x dcosx= xcosx |[π/2→0] + ∫[0→π/2] cosx dx= [sinx] |[0→π/2]= 1
楼上做的很好啊
