In triangle ABC AC = BC, AB = 15, AH- height, BH = 3. Find cos BAC.

Given: ∆ABS
AC = CB
AH – height
AB = 15
HB = 3
Find: cos of the angle ВАС.
Decision:
1. Consider ∆ABS: AC = CB => ∆ABS p \ b => angle B = angle A.
В ∆АНВ АН – height => angle Н = 90 °, НВ = 3, AB = 15;
2. Find the cos of the angle B = HB \ AB = 3 \ 15 = 1 \ 5 = 0.2 => cos of the angle B = cos of the angle A = 0.2.
Answer: 0.2.