Question

In isoceles ΔABC, |AB| = |AC|. If angle B = 55°, calculate angle A

Answer 1

∠A = 70°

Explanation:

Since the sides of the isosceles triangle AB and AC are congruent then

The base angles B and C are congruent and ∠B = ∠C = 55°

The sum of the 3 angles in a triangle = 180°

Subtract the sum of angles B and C from 180 for angle A, that is

∠A = 180° - (55 + 55)° = 180° - 110° = 70°