What does the exterior angle of a triangle equal?

The exterior angle of a triangle has a specific relationship with the triangle's interior angles. According to the exterior angle theorem, an exterior angle is equal to the sum of the two opposite interior angles. This relationship is derived from the properties of triangles and the fact that the sum of the interior angles in any triangle is always 180 degrees.

To visualize this, consider a triangle with one of its sides extended, forming an exterior angle. The two angles that are not adjacent to the exterior angle represent the interior angles at the two vertices that are opposite to the exterior angle. When you calculate the measure of the exterior angle, you are essentially adding the measures of these two opposite interior angles together.

This fundamental property is crucial in many geometrical proofs and applications, making it a key concept in understanding triangle properties.