∫ [x^2/(1+x^2) ](arctanx) dx=∫ (arctanx) dx - ∫ [1/(1+x^2) ](arctanx) dx= xarctanx - ∫ x/(1+x^2) dx -(1/2) ∫ d(arctanx)^2= xarctanx - (1/2)ln|1+x^2| -(1/2)(arctanx)^2 +C
