Precalculus (6th Edition) Blitzer

The trigonometric ratios are as follows: $\sin \theta= \dfrac{opposite}{hypotenuse}$ ; $\cos \theta= \dfrac{Adjacent}{hypotenuse}$ and $\tan \theta= \dfrac{Opposite}{Adjacent}$ Now, $\cot \theta= \dfrac{1}{\tan \theta}=\dfrac{1}{\dfrac{Opposite}{Adjacent}}$ So, our required answer is: $\cot \theta=-\dfrac{1}{0}$= Undefined