∫x^3arctanxdx=x^4/4arctanx-1/4∫x^4/(1 x^2)dx=1/4x^4arctanx-1/4∫(x^2-1 1/(1 x^2))dx=1/4x^4arctanx-1/12x^3 1/4x-1/4arctanx C看不懂啊好乱分部积分法∫ x³ arctanx dx= 1/4 ∫ arctanx dx⁴= x⁴/4 arctanx - 1/4 ∫ x⁴/(1+x²) dx= 1/4 x⁴ arctanx - 1/4 ∫ [ x²-1 + 1/(1+x²) ] dx= 1/4 x⁴ arctanx - 1/12 x³ + 1/4 x - 1/4 arctanx +C