Given :-
AB = AC
Then :-
This triangle is an isosceles triangle .
Let x be the value of ∠CAB . Then, ∠ABC will also have the same value as ∠CAB , since∠CAB and∠ABC are both the opposite base angles of an isosceles triangle .
An equation to find ∠ABC and ∠CAB :-






Which means that the measure of ∠ABC and ∠CAB both are equal to 60°, and this triangle is an equilateral triangle.
Therefore :-
