# What is cos if sin=-0.8 and is in Quadrant IV?r

May 4, 2018

$\cos \left(\arcsin \left(- \frac{4}{5}\right)\right)$

#### Explanation:

Since $- \frac{4}{5}$ isn't found on any of the special triangles, the best you can do is to isolate for theta and type it into your calculator. You know that cos will be positive since you are in quadrant IV.