Evaluate $\int \tan^{3} x\sec^{2} x\,dx$.

Explanation

1. 01

   Put $t = \tan x$, $dt = \sec^{2} x\,dx$.

2. 02

   $\int t^{3}\,dt = \frac{t^{4}}{4} = \frac{\tan^{4} x}{4} + C$.