Answer
$0$
Work Step by Step
I know that $\cos$ has a period of $360^\circ$, hence $\cos{\theta}=\cos{(\theta-2\pi)}.$ Thus $\cos{540^\circ}=\cos{(540^\circ-360^\circ)}=\cos{180^\circ}$
I know that $\tan$ is an odd function, which means $f(-\theta)=-f(\theta).$ Therefore $\tan{-45^\circ}=-\tan{45^\circ}$.
Thus: $\cos{540^\circ}-\tan{-45^\circ}=\cos{180^\circ}+\tan{45^\circ}=-1+1=0$.
