In this activity, we will be investigating angle sizes and types of angles. 

 

Here are a few important facts we need to know for our work with triangles!

 

A right angle is 90º

 

An acute angle is less than 90º

 

 

An obtuse angle is between 90º and 180º

 

 

A straight line angle is 180º

 

A reflex angle is between 180º and 360º

 

 

Triangles

A right-angled triangle has one 90º angle.

 

 

An isosceles triangle has two equal angles.

 

 

An equilateral triangle has three equal angles, each of size 60º

 

 

A scalene triangle has three different angles.

 

 

Let's try an example question. 

 

Example

Perry draws an angle of 72°

What type of angle is this?

 

Answer

Angles smaller than 90° are acute. 

Perry's angle is acute.

 

If you want to see this introduction again, just click on the red help button that will appear on the screen.

 

Let's get practising!