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