∫xarctanxdx 分部积分=(∫arctanxdx^2)/2=x^2arctanx|(0,1)/2 - ∫x^2darctanx/2=π/8 - ∫(x^2/1+x^2)dx/2=π/8 - ∫(1-1/(1+x^2))dx/2=π/8 - ∫dx/2 + ∫dx/(1+x^2)/2=π/8 - x/2|(0,1) + arctanx/2|(0,1)=π/8 ...