The Exterior, Interior and Remote Interior Angles
An exterior angle of a triangle, or any polygon, is formed by extending one of the sides of the triangle (or polygon).
In a triangle, each exterior angle has two remote interior angles (see picture below). The remote interior angles are just the two angles that are inside the triangle and opposite from the exterior angle.
The exterior angle is supplemental to the adjoining interior angle. Notice:
Since 46+134=180, these angles aresupplementary as is every exterior angle and its adjacent interior angle.
If the exterior angle,
1 = 110°what is m2?
Formula for Remote Interior Angles and Exterior Angles
As the picture below shows, an exterior angle (A) equals the sum of the remote interior angles.
To rephrase it, the angle ‘outside the triangle’ (exterior angle A) equals D + C (the sum of the remote interior angles).
Getting to know Math 