Exterior Angles of Triangles

Front

What is an exterior angle of a triangle?

Back

An exterior angle of a triangle is formed by one side of the triangle and the extension of an adjacent side. It is equal to the sum of the two opposite interior angles.

Front

What is the Exterior Angle Theorem?

Back

The Exterior Angle Theorem states that the measure of an exterior angle of a triangle is equal to the sum of the measures of the two non-adjacent interior angles.

Front

If one interior angle of a triangle is 50° and another is 60°, what is the measure of the exterior angle at the vertex of the 60° angle?

Back

The exterior angle is 50° + 60° = 110°.

Front

How do you find the measure of a missing angle in a triangle?

Back

To find a missing angle in a triangle, use the fact that the sum of all interior angles in a triangle is 180°. Subtract the sum of the known angles from 180°.

Front

What is the relationship between an exterior angle and its adjacent interior angle?

Back

The exterior angle is equal to the sum of the two opposite interior angles, and it is supplementary to its adjacent interior angle.

Front

If the exterior angle of a triangle is 120°, what are the possible measures of the two opposite interior angles?

Back

The two opposite interior angles must sum to 120°. For example, they could be 60° and 60°, or 70° and 50°.

Front

What is the measure of an exterior angle if the two opposite interior angles are 40° and 70°?

Back

The measure of the exterior angle is 40° + 70° = 110°.

Front

In a triangle, if one angle is 90°, what is the measure of the exterior angle at that vertex?

Back

The exterior angle is 90° + the measure of the other non-adjacent angle.

Front

What is the sum of the exterior angles of any polygon?

Back

The sum of the exterior angles of any polygon is always 360°, regardless of the number of sides.

Front

If angle A is 36° and angle B is 56°, what is the measure of the exterior angle at angle B?

Back

The exterior angle at angle B is 36° + 56° = 92°.