Exterior Angles in 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.

Tags

CCSS.8.G.A.5

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.

Tags

CCSS.8.G.A.5

Front

If angle A = 50° and angle B = 60°, what is the measure of the exterior angle at vertex C?

Back

The exterior angle at vertex C is 110° (50° + 60°).

Tags

CCSS.8.G.A.5

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.

Tags

CCSS.8.G.A.5

Front

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

Back

The exterior angle is supplementary to its adjacent interior angle, meaning they add up to 180°.

Tags

CCSS.8.G.A.5

Front

If the exterior angle is 145°, what is the measure of the adjacent interior angle?

Back

The adjacent interior angle is 35° (180° - 145°).

Tags

CCSS.8.G.A.5

Front

In triangle ABC, if angle A = 70° and angle B = 40°, what is the measure of angle C?

Back

Angle C is 70° (180° - 70° - 40°).

Tags

CCSS.8.G.A.5

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°.

Front

If angle A = 90° in triangle ABC, what can you say about the exterior angle at vertex A?

Back

The exterior angle at vertex A is equal to the sum of the other two angles, which must also be 90°.

Tags

CCSS.8.G.A.5

Front

How can you use the Exterior Angle Theorem to solve for x in a triangle?

Back

Set the exterior angle equal to the sum of the two non-adjacent interior angles and solve for x.

Tags

CCSS.8.G.A.5