Question

prove that the wach angle of an equilateral triangle is 60 degree

Answer 1

Given:- Triangle ABC in which AB=BC=CA
To prove:- Angle A = Angle B = Angle C = 60 degree
Proof :- AB=AC
Therefore, Angle A = Angle B (Angles opp. equal sides are equal)........(i)
AB=BC
Therefore, Angle A = Angle C(Angles opp. equal sides are equal)...........(ii)

From (i) and (ii),
Angle A = Angle B = Angle C

A+B+C=180 degree (angle sum property of triangles)
3A=180
A=60
Therefore, Angle A = Angle B = Angle C = 60 degrees