Triangle Sum Theorem and Exterior Angle Theorem

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 degrees.

Front

If one angle of a triangle is 90 degrees and another is 45 degrees, what is the measure of the third angle?

Back

The third angle measures 45 degrees, since 90 + 45 + 45 = 180.

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 exterior angle of a triangle measures 100 degrees, and one of the opposite interior angles measures 40 degrees, what is the measure of the other opposite interior angle?

Back

The other opposite interior angle measures 60 degrees, since 100 = 40 + x, where x is the unknown angle.

Front

How do you find the measure of the third angle in a triangle if two angles are known?

Back

Subtract the sum of the two known angles from 180 degrees.

Front

What is the measure of the third angle in a triangle with angles measuring 30 degrees and 50 degrees?

Back

The third angle measures 100 degrees, since 180 - (30 + 50) = 100.

Front

If two angles in a triangle are 45 degrees and 75 degrees, what is the measure of the third angle?

Back

The third angle measures 60 degrees, since 180 - (45 + 75) = 60.

Front

What is the relationship between an exterior angle and the two opposite interior angles?

Back

The exterior angle is equal to the sum of the two opposite interior angles.

Front

If an exterior angle measures 120 degrees, and one of the opposite interior angles measures 50 degrees, what is the measure of the other opposite interior angle?

Back

The other opposite interior angle measures 70 degrees, since 120 = 50 + x, where x is the unknown angle.

Front

What is the sum of the angles in any triangle?

Back

The sum of the angles in any triangle is always 180 degrees.