Types of angles

In a nutshell

There are four main way to classify angles: acute, right, obtuse and reflex. Angles can also be represented using three-letter notation.

Types of angles

Here are the four types of angles you need to know:

NAME	DESCRIPTION	DIAGRAM
Acute angles	Angles that are less than $90\degree$
Right angles	Angles that are exactly $90\degree$
Obtuse angles	Angles that are between $90\degree$ and $180\degree$
Reflex angles	Angles that are between $180\degree$ and $360\degree$

Three-letter angle notation

Three-letter angle notation is a way of referring to angles in shapes. It is represented using the angle symbol ( $\angle$ ) followed by three capital letters. The angle being referred to is the middle letter.

Example

Express the given angle in three-letter notation:

Maths; Lines and angles; KS3 Year 7; Types of angles

The angle is at the point $V$ , and the lines extend to the points $A$ and $B$ .

Hence, the angle is written as $\angle AVB$ in three-letter notation.

The given angle is written as $\underline{\angle AVB}$ .

Note: It is also acceptable to write the angle as $\angle BVA$ .