Sum and Difference Formulas Question?

Question

Find the exact value of the following under the given conditions:

cos a(alpha) = 8/17, a(alpha) lies in quadrant IV, and sin b(beta) = -1/2, b(beta) lies in quadrant III.

Answer 1

cos α = 8 / 17
α = 360° - 61.9°
α = 298.1 °

sin β = (-1/2)
β = 180° + 30°
β = 210°