Answer:
5
Step-by-step explanation:
This is a pretty simple question to answer, the one step that needs to be done is divide 78.5 by 15.7. You should come up with 5.
Recall the angle sum identities:


Now,

Divide through numerator and denominator by
to get

Next, we use the fact that
lie in the first quadrant to determine that


So we then have


Finally,

Keep change flip then simplify or divide if needed