Question

∆ABC is isosceles with legs AB and AC. If AC = 6 cm, and the perimeter is 15 cm, calculate m∠B.

Answer 1

m∠B = 75.5°

Explanation:

Since AC = 6, then AB = 6 and BC = 15-6-6 = 3

The altitude from A bisects side BC. Let the point of intersection of the altitude and BC be point D. Then BD = 1.5

Cos B = 1.5/6

m∠B = arcccos (1.5/6)

m∠B = 75.5°