Question

In triangle ABC, a = 2, c = 6, and cos B = . Find b.

Answer 1

Use Law of Cosines, which is ß² = α² + c² - 2αccos(B) where <B is opp. to side ß.

Let α = 2, c = 6 and cos(B) = 1/6, so

ß = √(2² + 6² - 2(2)(6)(1/6))

= √(4 + 36 - 4)

= √36 = 6