Question

Triangle ABC has 2 known sides. A = 7, b = 5. Angle C = 24.63. What is the value of side c, correct to one decimal place?

Answer 1

We use the Law of Cosines:
side c² = a² + b² -2ab • cos(C)
side c^2 = 7^2 + 5^2 -(2*7*5*cosine(24.63))
side c^2 = 49 + 25 -(70 * 0.90902)
side c^2 = 74 - 63.6314
side c^2 = 10.3686
side c = 3.22

Source:
http://www.1728.org/trigtut2.htm