Answer:
m∠B = 75.5°
Step-by-step 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°
