5.7 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

State 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 60°, what is the measure of the exterior angle adjacent to the 60° angle?

Back

The exterior angle is 40° + 60° = 100°.

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 interior and exterior angles in a triangle?

Back

The exterior angle is equal to the sum of the two opposite interior angles.

Front

If angle A = 50° and angle B = 70°, what is the measure of angle C?

Back

Angle C = 180° - (50° + 70°) = 60°.

Front

What is the measure of an exterior angle if the two opposite interior angles are 30° and 50°?

Back

The exterior angle = 30° + 50° = 80°.

Front

If an exterior angle measures 120°, what are the 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°.

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

How can you determine if a triangle is valid based on its angles?

Back

A triangle is valid if the sum of its interior angles equals 180°.