Question

prove that every angle of an equailateral triangle is of 60 degree

Answer 1

its easy just use isoceles triangle property

Answer 2

now
we know that the angles opposite to equal sides are equal to each other.
suppose there is a triangle ABC in which sides ab bc and ac are equal
So now the angles opposite to them will also be equal to each other
that means all the angles are equal to each other now
Let the each equal angle be x.

by angle sum property of a triangle

x + x + x = 180°

3x = 180

x = 60°

hope this helps...