How do you justify an inscribed equilateral triangle in geometry?

Answer 1

If you mean properties of an equilateral triangle then some of them are:-

It has 3 equal sides

It has 3 equal interior angles that add up to 180 degrees

It has 3 lines of symmetry

It will tessellate leaving no gaps or overlaps

Its perimeter is the sum of its 3 sides

It can fit perfectly into a circle

Its area is: 0.5*base*perpendicular height