Mark M. answered 12/01/19
Retired Math prof with teaching and tutoring experience in trig.
Using the Law of Sines, sin10° / 8 = sinC / 9
9sin10° = 8sinC
sinC = (9sin10°) / 8 = 0.195
The sine function is positive in quadrants 1 and 2, So, there are 2 possibilities for ∠C:
∠C = Sin-1(0.195) or 180° - Sin-1(0.195) = 11.2° or 168.8°
There are two triangles:
First triangle: ∠B = 10°, ∠C = 11.2°, ∠A = 158.8°, b = 8, c = 9. Find side a by Law of Sines.
Second triangle: ∠B = 10°, ∠C = 168.8°, ∠A = 1.2°, b = 8, c = 9, Find side a using Law of Sines.