## Precalculus: Mathematics for Calculus, 7th Edition

$\cos t\csc t=\cot t$
$\cos t\csc t$ Substitute $\csc t$ with $\dfrac{1}{\sin t}$ and simplify: $\cos t(\dfrac{1}{\sin t})=\dfrac{\cos t}{\sin t}=\cot t$