## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$-1$
As we can see from the attached graph (please refer to the green one), as $x$ gets closer and closer to $0$ from the left and the right, the value of the function (the $y$-value) gets closer and closer to $-1$. Thus, the limit is $-1$.