An equilateral triangle is a triangle? in which all three sides have the same length.
An equivalent condition is that all three angles are the same.
As the angles in a triangle? add up to $180^\circ$, that all angles are the same means that they must each be $60^\circ$.
Equilateral triangles have three lines of symmetry? passing through the midpoint? of each side and the opposite angle.
All equilateral triangles are similar?.
A triangle with two angles of $60^\circ$ must be equilateral.