用分步积分法啊∫(x^2)*arctanxdx=1/3∫arctanxdx^3=1/3x^3arctanx-1/3∫x^3/(1+x^2)dx=1/3x^3arctanx-1/6∫x^2/(1+x^2)dx^2=1/3x^3arctanx-1/6∫[1-1/(1+x^2)]dx^2=1/3x^3arctanx-1/6x^2+1/6ln(1+x^2)+C...