## The Lesson

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.

## Dictionary Definition

The Oxford English Dictionary defines an obtuse angle as "a plane angle: greater than 90 degrees and less than 180 degrees."## Real Examples of Obtuse Angles

The angles below are all obtuse angles:## Interactive Game on the Types of Angles

## 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".