I'm just going to assume I've constructed an equilateral triangle, so Triangle ABC is equilateral. and if it's equilateral, that means all of it's sides are equal, and lets say that it has an equilateral with sides of length x. so this is going to be x this is going to be x, and this is going to be x. we also know, based on what we seen from equilateral triangles before, that the measures of all of these angles are going to be 60 degrees.