# What Is an Obtuse Angle? (Mathematics Lesson)

# What Is an Obtuse Angle?

An obtuse angle is an angle greater than 90° and less than 180°.An obtuse angle is greater than a right angle and less than a straight line.

# Real Examples of Obtuse Angles

The angles below are all obtuse angles:##### Curriculum

##### Interactive Test

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##### Note

**WHAT'S IN A NAME?**

Obtuse comes from the Latin word 'obtusus' meaning "blunt".

An obtuse angle makes a blunt point.

# EUCLID AND OBTUSE ANGLES

Euclid defines angles in his book,*Elements*.

**Definition 11:**"An obtuse angle is an angle greater than a right angle".