## Precalculus: Mathematics for Calculus, 7th Edition

$\cos t * tan t=\sin t$
$\cos t\tan t$ Change $\tan t$ with $\dfrac{\sin t}{\cos t}$: $\cos t\tan t=\cos t(\dfrac{\sin t}{\cos t})=...$ Simplify: $\cos t\tan t=\cos t(\dfrac{\sin t}{\cos t})=\sin t$