# Exterior Angle Property

## ABOUT:

The Angle formed by a side with its extended adjacent side of a triangle is called an exterior angle of the triangle.

**Exterior Angle Property states** that the measure of exterior angles of a triangle is equal to the sum of its two interior opposite angles.

A triangle has three corners, called *vertices*.

The sides of a triangle (line segments) that come together at a vertex form two angles

Only one of these angles contains the third side of the triangle in its interior, and this angle is called an *interior angle* of the triangle.

In the figure below, the angles *∠**ABC*, *∠**BCA* and *∠**CAB* are the three interior angles of the triangle.

An *exterior angle* is formed by extending one of the sides of the triangle;

The angle between the extended side and the other side is the exterior angle. In the figure below, angle *∠**ACD* is an exterior angle.

**Properties**

- An exterior angle of a triangle is equal to the sum of the opposite interior angles.
- If the equivalent angle is taken at each vertex, the exterior angles always add to 360° .