(π,0) ∫ xsinx dx
=(π,0) ∫ -x dcosx
= -xcosx | (π,0) + (π,0) ∫cosxdx
= -(0-πcosπ) + sinx | (π,0)
= -π
按常规,应该是 0 到 π 如果是,则结果应是 π(0,π/2) ∫ xsinx dx=(0,π/2) ∫ -x dcosx= -xcosx | (0,π/2) + (0,π/2) ∫cosxdx= 0 + sinx | (0,π/2)= 1