Answer
$20^o$
Work Step by Step
RECALL:
The following are the means on how to find the reference angle of an angle $\theta$ based on its position:
(1) Quadrant I: $\theta$ (itself)
(2) Quadrant II: $180^o-\theta$
(3) Quadrant III: $\theta - 180^o$
(4) Quadrant IV: $360^o-\theta$
$160^o$ is in Quadrant II.
Thus, using forrmula (2) above gives:
reference angle of $160^o$ = $180^o-160^o=20^o$
