## Trigonometry (10th Edition)

$cot 1800^{\circ}= undefined$
1. What we know about 1800 degree angle $\theta=0^{\circ}$ (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: $\cot\theta=\frac{x}{y}=\frac{1}{0}=undefined$