Answer
$sin(-\frac{5\pi}{4})=\frac{\sqrt 2}{2}$
$cos(-\frac{5\pi}{4})=-\frac{\sqrt 2}{2}$
$tan(-\frac{5\pi}{4})=-1$
Work Step by Step
Let $θ'$ be the reference angle. We must have that $0\leqθ'\lt2\pi$
$θ'=θ+n·2\pi$, where $n$ is an integer.
$θ'=-\frac{5\pi}{4}+1·2\pi=\frac{3\pi}{4}$
$sin(-\frac{5\pi}{4})=sin\frac{3\pi}{4}=\frac{\sqrt 2}{2}$
$cos(-\frac{5\pi}{4})=cos\frac{3\pi}{4}=-\frac{\sqrt 2}{2}$
$tan(-\frac{5\pi}{4})=tan\frac{3\pi}{4}=-1$
