用分部积分法,即∫udv=uv-∫vdu∫ln(1+x^2)dx=x*ln(1+x^2)-∫x*d[ln(1+x^2)]=x*ln(1+x^2)-∫x*[2x/(1+x^2)]dx=x*ln(1+x^2)-2∫[x^2/(1+x^2)]dx=x*ln(1+x^2)-2∫[(1+x^2)-1]/(1+x^2)dx=x*ln(1+x^2)-2∫[1-(1/1+x^2)]d...