Use the Law of Sines to find the missing angle of the triangle.

Find mB given that c=16, a=17, and mA=73.

A. 0.0°

B. 42.8°

C. 64.2°

D. 180.0°

Answer: option B. 42.8°

Explanation:

1) Law of sines

sinA / a = sinB / B = sinC / c

2) You know c = 16, a, = 17 and A = 73°, so you can find C:

sinC / c = sinA / a ⇒ sinC = sinA * c / a = sin (73°) * 16 / 17 = 0.900

⇒C = arcsin (0.900) = 64.16°

3) Since the sum of the 3 angles is 180°, you calculate B as:

B = 180° - A - C = 180° - 73° - 64.16° = 42.84°