Question

in triangle ABC, BC=AB and angle B= 80, then angle A=?

Answer 1

see the attachment for sol.

Answer 2

Answer:

In triangle ABC, BC=AB and angle B= 80, then angle A = 50

Solution:

Given that in triangle ABC, BC = AB which means ABC is an isosceles triangle.

We know the sum of angles in a triangle is 180°. Since it is an isosceles triangle the measure of two angles will be same. Let ∠A = x and ∠c = x

We know,

Sum of all angles = 180°

x+x+80° = 180°

2x= 180°-80°

2x=100°

x= $\frac{100}{2}$ = 50

Thus the measure of ∠A = 50°