解:
设
$\displaystyle t=\arcsin x,dt=\frac{1}{\sqrt{1-x^2}}dx,$
则
$\displaystyle I=\int \frac{(1+x^2)\arcsin x}{x\sqrt{1-x^2}}dx=\int \frac{(1+\sin ^2t)t}{\sin t}dt=\int \frac{(1+\sin ^2t)(\pi+t)}{-\sin t}dt,(t=\pi+t)$
$\begin{align*}\therefore I&=-\frac{1}{2}\int \frac{(1+\sin ^2t)\pi}{\sin t}dt\\\\&=-\frac{\pi}{2}(\int \frac{1}{\sin t}dt+\int \sin tdt)\\\\&=-\frac{\pi}{2}(\frac{1}{2}\ln\frac{1-\cos t}{1+\cos t}-\cos t)+C\\\\&=-\frac{\pi}{4}\ln\frac{1-\cos t}{1+\cos t}+\frac{\pi}{2}\cos t+C\\\\&=-\frac{\pi}{4}\ln\frac{1-\sqrt{1-x^2}}{1+\sqrt{1-x^2}}+\frac{\pi}{2}\sqrt{1-x^2}+C.\end{align*}$