∫㏑(1＋t^2)dt
=tln(1+t^2) - 2∫t^2/(1＋t^2)dt
=tln(1+t^2) - 2∫(t^2+1)/(1＋t^2)dt +2∫dt/(1＋t^2)
=tln(1+t^2) - 2t +2arctan(t) + C