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 70°, what is the measure of the exterior angle adjacent to the 70° angle?

Back

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

Front

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

Back

To find a missing angle, use the Exterior Angle Theorem: subtract the sum of the two known interior angles from the exterior angle.

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

Back

Let the opposite interior angles be x and y. Then, x + y = 120°.

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, while the adjacent interior angle is not included in this sum.

Front

If angle A = 50° and angle B = 60°, what is the measure of angle C in triangle ABC?

Back

Angle C = 180° - (50° + 60°) = 70°.

Front

What is the measure of an exterior angle if the two opposite interior angles are 45° and 55°?

Back

The exterior angle = 45° + 55° = 100°.

Front

How can you verify the Exterior Angle Theorem using a triangle?

Back

Draw a triangle, extend one side, and measure the exterior angle and the two opposite interior angles to confirm their sum.