Angle Relationships

Front

What is an angle?

Back

An angle is formed by two rays (sides) that share a common endpoint (vertex).

Front

What is the measure of a right angle?

Back

A right angle measures exactly 90°.

Front

What is an acute angle?

Back

An acute angle is an angle that measures less than 90°.

Front

What is an obtuse angle?

Back

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

Front

What is a straight angle?

Back

A straight angle measures exactly 180°.

Front

What are complementary angles?

Back

Complementary angles are two angles whose measures add up to 90°.

Front

What are supplementary angles?

Back

Supplementary angles are two angles whose measures add up to 180°.

Front

What are vertical angles?

Back

Vertical angles are the angles opposite each other when two lines intersect. They are always equal.

Front

If ∠A and ∠B are complementary, and ∠A measures 30°, what is the measure of ∠B?

Back

∠B = 60° (because 30° + 60° = 90°).

Front

If ∠C and ∠D are supplementary, and ∠C measures 110°, what is the measure of ∠D?

Back

∠D = 70° (because 110° + 70° = 180°).