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

$-\dfrac{\sqrt{3}}{2}$
The sine is an odd function, so $\sin{(-\theta)} = - \sin{\theta}$ Thus, $\sin{\left(- \dfrac{\pi}{3} \right) } = - \sin{\left( \dfrac{\pi}{3} \right) } = \boxed{-\dfrac{\sqrt{3}}{2}}$