Recognise Right Angles

In this activity, we'll take a look at types of angles.

A right angle is an angle that is equal to 90°.  

Here is a right angle.

We can see it's marked with a rectangle corner marker.

If you see an angle marked with a square or rectangle, it's a right angle.

An acute angle is an angle that is smaller than 90°.  

Here is an acute angle.

An obtuse angle is an angle that is larger than 90°.  

Here is an obtuse angle.

Let's look at an example question. 

Example

How many of the angles shown below are acute?

Answer

An acute angle is smaller than a right angle. 

Three of the triangles shown are acute (smaller than a right angle). 

Now it's your turn to have a go at some questions.