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 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 is 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 non-adjacent interior angles.

Front

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

Back

The other non-adjacent interior angle measures 70 degrees, since 120 = 50 + x, thus x = 70.

Front

What is the formula to find the missing angle in a triangle when two angles are known?

Back

The formula is: Missing Angle = 180 - (Angle 1 + Angle 2).

Front

In a triangle, if two angles are 30 degrees and 60 degrees, what is the third angle?

Back

The third angle is 90 degrees, since 30 + 60 + 90 = 180.

Front

How do you find the measure of an angle in a triangle if you know the measures of the other two angles?

Back

You subtract the sum of the known angles from 180 degrees.

Front

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

Back

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

Front

If a triangle has angles measuring 40 degrees and 70 degrees, what type of triangle is it?

Back

It is an acute triangle, as all angles are less than 90 degrees.

Front

What is the sum of the angles in any triangle?

Back

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