Types of angles
Select Lesson
Statistics
Probability
Trigonometry
Properties of shapes
Shapes
Rates of change
Other graphs
Straight line graphs
Formulae and equations
Algebraic manipulation
Fractions, decimals and percentages
Number calculations
Explainer Video
Summary
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 |  |
| Right angles | Angles that are exactly |  |
| Obtuse angles | Angles that are between and |  |
| Reflex angles | Angles that are between and |  |
Three-letter angle notation
Three-letter angle notation is a way of referring to angles in shapes. It is represented using the angle symbol () followed by three capital letters. The angle being referred to is the middle letter.
Example
Express the given angle in three-letter notation:
The angle is at the point , and the lines extend to the points and .
Hence, the angle is written as in three-letter notation.
The given angle is written as .
Note: It is also acceptable to write the angle as .
FAQs - Frequently Asked Questions
What is a reflex angle?
A reflex angle is an angle that is between 180 and 360 degrees.
How do you write letters in three-letter angle notation?
The middle letter refers to where the angle is and the other two letters refer to which lines to draw the angle from.
What are the 4 types of angles?
The four types of angles are: acute, right, obtuse, reflex.