# Equilateral Triangle

## Equilateral Triangle

Triangle whose three sides are congruent.

### Property

A triangle is an equilateral triangle if its three angles are congruent and they all measure 60°.

### Formula

The formula to calculate the area A of an equilateral triangle is: $$A=\frac{c^{2}}{4}\sqrt{3}$$

The formula to calculate the radius r of the circle circumscribed about an equilateral triangle is: $$r=\frac{c}{3}\sqrt{3}$$

The formula to calculate the radius r of the circle inscribed in an equilateral triangle is: $$r=\frac{c}{6}\sqrt{3}$$

### Example

This is an equilateral triangle: