>>472
x/{(x+1)(x^2+1)} =(x+1)/(2(x^2+1)) -1/(2(x+1)) より
∫ x/{(x+1)(x^2+1)} dx
=∫x/(2(x^2+1))dx+∫1/(2(x^2+1))dx -∫1/(2(x+1))
=(1/4)*(log(x^2+1)+(1/2)*arctanx -(1/2)log(x+1)