D1: Classifying Angles

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

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

A right angle is an angle that measures exactly 90 degrees.

A straight angle is an angle that measures exactly 180 degrees.

A reflex angle is an angle that measures more than 180 degrees but less than 360 degrees.

An acute angle can be identified as being sharp and less than 90 degrees.

An obtuse angle can be identified as being wide and more than 90 degrees but less than 180 degrees.

A right angle can be identified by its square corner, measuring exactly 90 degrees.

A straight angle can be identified as a straight line, measuring exactly 180 degrees.

A reflex angle can be identified as being larger than a straight angle, measuring more than 180 degrees.