Triangle Sum and Exterior Angle Theorems

Front

What is the Triangle Sum Theorem?

Back

The Triangle Sum Theorem states that the sum of the interior angles of a triangle is always 180°.

Front

If one angle of a triangle is 70° and another is 60°, what is the measure of the third angle?

Back

The third angle is 50° (180° - 70° - 60° = 50°).

Front

What is an exterior angle of a triangle?

Back

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

Front

State the Exterior Angle Theorem.

Back

The Exterior Angle Theorem states that the measure of an exterior angle is equal to the sum of the measures of the two remote interior angles.

Front

If an exterior angle measures 130°, what are the measures of the two remote interior angles if one is 50°?

Back

The other remote interior angle measures 80° (130° - 50° = 80°).

Front

What are remote interior angles?

Back

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

Front

If Angle W is 40°, what are the measures of the remote interior angles?

Back

If Angle W is 40°, the sum of the remote interior angles must be 140° (180° - 40° = 140°).

Front

How do you find the measure of an unknown angle in a triangle?

Back

To find an unknown angle, subtract the sum of the known angles from 180°.

Front

What is the relationship between the angles in a right triangle?

Back

In a right triangle, one angle is 90°, and the sum of the other two angles is 90°.

Front

If two angles of a triangle are 45° and 55°, what is the measure of the third angle?

Back

The third angle is 80° (180° - 45° - 55° = 80°).