Angles in a Triangle

Front

What is the Triangle Sum Theorem?

Back

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

Front

What is an 'Acute' Angle?

Back

An angle that measures less than 90°.

Front

What is an 'Obtuse' Angle?

Back

An angle that measures more than 90° but less than 180°.

Front

What is a 'Right' Angle?

Back

An angle that measures exactly 90°.

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 opposite interior angles.

Front

If angle A = 40° and angle B = 60°, what is angle C in triangle ABC?

Back

Angle C = 180° - (40° + 60°) = 80°.

Front

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

Back

Use the Triangle Sum Theorem: subtract the sum of the known angles from 180°.

Front

What is the relationship between the angles in a triangle and its sides?

Back

In a triangle, the larger the angle, the longer the opposite side.

Front

If angle R > angle S > angle T, what can be said about the sides opposite these angles?

Back

The side opposite angle R is the longest, followed by the side opposite angle S, and the side opposite angle T is the shortest.