Question

If a = 4, b = 5, and c = 6, how do you solve the triangle?

Answer 1

Use identity:

`c^2 = a^2 + b^2 - 2ab.cos C`
36 = 25 + 16 - 40.cos C --> cos C = 5/40 = 0.125 --> C = 82.82 deg

sin^20 C = 1 - cos^2 C = 0.98 -> sin C = 0.99

Next, use trig identity:`sin A/a = sin C/c`

`sin A = 4((0.99)/6) =`0.66 -> A = 41.30

B = 180 - 41.30 - 82.82 = 55.88