Answer
$-\sqrt 5$.
Work Step by Step
1. Let $tan^{-1}(-2)=t$, we have $tan(t)=-2$ and $t$ in quadrant IV.
2. Let $x=2, y=-1$, we have $r=\sqrt {2^2+(-1)^2}=\sqrt 5$.
3. Thus $csc(tan^{-1}(-2))=csc(t)=\frac{r}{y}=-\sqrt 5$.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.