3.2 Exterior Angle Theorem

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 40° and another is 70°, what is the measure of the exterior angle?

Back

The exterior angle is 40° + 70° = 110°.

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, not the adjacent one.

Front

How do you find the measure of an unknown angle using the Exterior Angle Theorem?

Back

To find an unknown angle, add the measures of the two non-adjacent interior angles.

Front

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

Back

The sum of the two non-adjacent interior angles must equal 120°; for example, 60° and 60°.

Front

What is the sum of the interior angles of a triangle?

Back

The sum of the interior angles of a triangle is always 180°.

Front

If one interior angle of a triangle is 30° and another is 50°, what is the measure of the third angle?

Back

The third angle is 180° - (30° + 50°) = 100°.

Front

In a triangle, if one exterior angle measures 94°, what are the measures of the two non-adjacent interior angles?

Back

The two non-adjacent interior angles must sum to 94°; for example, 45° and 49°.

Front

What is the formula to calculate the exterior angle of a triangle?

Back

Exterior Angle = Interior Angle 1 + Interior Angle 2.

Front

If an exterior angle is 86°, what are the possible measures of the two non-adjacent interior angles?

Back

The two non-adjacent interior angles must sum to 86°; for example, 40° and 46°.