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 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 an unknown angle in a triangle using exterior angles?

Back

To find an unknown angle, use the Exterior Angle Theorem: the exterior angle equals the sum of the two opposite interior angles.

Front

What is the relationship between the interior angles and exterior angles of a triangle?

Back

The sum of the measures of the interior angles of a triangle is always 180°, and each exterior angle is equal to the sum of the two opposite interior angles.

Front

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

Back

The two opposite interior angles must sum to 120°.

Front

What is the sum of all exterior angles of a triangle?

Back

The sum of all exterior angles of a triangle is always 360°.

Front

If one exterior angle of a triangle is 150°, what is the measure of the adjacent interior angle?

Back

The adjacent interior angle is 180° - 150° = 30°.

Front

How can you use algebra to solve for an unknown angle in a triangle using exterior angles?

Back

Set up an equation using the Exterior Angle Theorem: if x is the unknown angle, then x = angle1 + angle2.

Front

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

Back

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