# What is an equilateral triangle? Definition and examples

An equilateral triangle is a type of triangle that has all sides of equal length and all angles of equal measure.

## Some interesting properties of an equilateral triangle

• An equilateral triangle has three lines of symmetry. Each line of symmetry starts from a vertex and is perpendicular to the side opposite the vertex
• Since all sides of an equilateral triangle are equal, the perimeter is just three times the length of one of its sides
• Since the sum of the angles in a triangle is equal to 180 degrees, each angle in an equilateral triangle measures 60 degrees
• Each line of symmetry divides an equilateral triangle into two congruent triangles

## Real-life examples of equilateral triangles

The Star of David made by two interlocking equilateral triangles is a good real-life example.

The traffic sign below warning someone of a danger is an equilateral triangle

The rack used to place billiard balls in their starting positions is shaped like an equilateral triangle