令x=tant
dx=sec²tdt
所以
原式=∫e^t/(sec²t)^(3/2) ·sec²tdt
=∫cost ·e^tdt
=∫costde^t
=e^t ·cost-∫e^tdcost
=e^t ·cost+∫sint e^tdt
=e^t ·cost+∫sint de^t
=e^t ·cost+sint e^t-∫e^tdsint
=e^t(sint+cost)-∫e^t costdt
所以
∫cost ·e^tdt=1/2 e^t(sint+cost)+c
所以
原式=1/2 e^arctant ·(x/√(1+x²)+1/√(1+x²))+c