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: