#### Answer

$v(t)=f\circ g(t)$ for
$g(t)=t^{2}$ and $f(t)=\sec t\tan t$

#### Work Step by Step

$f\circ g(t)=f[g(t)]$
Rule of thumb: Ask yourself
what would be the last operation if we used a calculator, step by step?
(Answer: If R$=t^{2}$ was the current result, we would calculate $\sec t\tan t$)
$f(t)=\sec t\tan t$
$v(t)=f(t^{2})$
So, if
$g(t)=t^{2}$ and $f(t)=\sec t\tan t$,
then
$v(t)=f\circ g(t)$