Answer
$-\frac{\sqrt3}{2}$
Work Step by Step
We know that $\sin$, $\csc$, $\tan$ are odd functions, which means $f(-\theta)=-f(\theta).$
We also know that $\cos$, $\sec$, are even functions, which means $f(-\theta)=f(\theta).$
Therefore
$\sin{(-60^{o})}=-\sin{(60^{o})}=-\frac{\sqrt3}{2}.$