Answer
$cot (540^{\circ})= undefined$
Work Step by Step
1. What we know about 540 degree angle
$\theta=180^{\circ}$ (because it is a co-terminal angle and values of x and y will be the same)
$x=-1$
$y=0$
$r=1$
2. Substitute in:
$\cot\theta=\frac{x}{y}=\frac{-1}{0}=undefined$
