∫x^2 * arctanxdx＝1/3×∫arctanxd(x^3)＝1/3×x^3×arctanx－1/3×∫x^3/(1+x^2)＝1/3×x^3×arctanx－1/3×∫(x^3+x-x)/(1+x^2)＝1/3×x^3×arctanx－1/3×∫xdx＋1/3×∫x/(1+x^2)＝1/3×x^3×arctanx－1/6×x^...