Question

In triangle ABC, a = 3, b = 5, and c = 7. Find the approximate value of angle A.

Answer 1

21.8° (22° to the nearest degree)

Explanation:

Using cosine law:

a² = b² + c² - 2bc(cosA)

3² = 5² + 7² - 2(5)(7)cosA

cosA = 13/14

A = 21.7867893

Approximately angle: 22°