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 opposite interior angles.

Front

If one interior angle of a triangle is 40° and another is 60°, what is the measure of the exterior angle?

Back

The exterior angle is 100° (40° + 60°).

Front

What is an exterior angle in a triangle?

Back

An exterior angle is formed by one side of the triangle and the extension of an adjacent side.

Front

Identify the exterior angle in the following triangle: (provide a diagram with angles labeled a, b, c, d)

Back

Angle d is the exterior angle.

Front

What are opposite interior angles?

Back

Opposite interior angles are the two angles inside a triangle that are not adjacent to a given exterior angle.

Front

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

Back

The opposite interior angles must sum to 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, not the adjacent interior angle.

Front

Solve for x: If one interior angle is 70° and the exterior angle is x, what is x?

Back

x = 110° (70° + 40°).

Front

Which angle is the exterior angle in this triangle? (provide a diagram with angles labeled)

Back

The angle formed by extending one side of the triangle.

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°.