先求原函数 分部积分∫arctanx/x^2dx = - ∫ arctanx d1/x = - (1/x) arctanx + ∫ dx / [x(1+x^2)] = - (1/x) arctanx + ∫x / [x^2(1+x^2)] dx = - (1/x) arctanx +1/2 ∫ 1/ [x^2(1+x^2)] dx^2 = - (1/x) arctanx...