← Back to Test

Problem 3 - Entrance Test

In triangle ABC angle A = 60°, side b = 5, side c = 8. Find the length of side a.

Correct: A

By the Law of Cosines: a² = b² + c² - 2bc cos A = 25 + 64 - 2·5·8·cos 60° = 89 - 80·0.5 = 89 - 40 = 49. Thus a = 7.