Answer:
cos theta = adja/ hypo
adja=8
hypo=17
cos theta= 8/17=0.47
theta= cos^-1 0.47
theta=1.0815
to fine missing side, use Pythagoras
hypo²= oppo² + adja²
17²= oppo² + 8²
289-64=oppo²
oppo²=225
oppo=15
