Answer
$2$
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,
$\sec(-60^{o})=\sec(60^{o})=\dfrac{1}{\cos(60^{O})}=\dfrac{1}{\frac{1}{2}}=2$
