Question

show that the angle of an equilateral tringalare 60 degree each

Answer 1

triangle A B C = 180 degrees 

angle AB + Angle BC + Angle AC = 180 degrees 

in equilateral triangle all sides are equal and hence all angles are equal. Hence AB=BC=AC ( from 1)

so ,
3AB=180 degrees (as AB=BC=CA)
AB=180/3 degrees 

so, Angle AB = 60 degrees 

Hence proofed
angle AB = Angle BC = Angle AC = 60 degrees