令x=tant,则dx=sec^2tdt原式=∫(tant*e^t)/sec^3t*sec^2tdt=∫sint*e^tdt=∫sint*d(e^t)=sint*e^t-∫e^t*costdt=sint*e^t-∫cost*d(e^t)=sint*e^t-cost*e^t-∫e^t*sintdt即∫sint*e^tdt=e^t*(sint-cost)/2+C原式=e^(arctanx)*[(x-1)/√(1+x^2)]+C,其中C是任意常数