In this activity, we will be investigating angles and identifying which type of angle they are.

An angle measures the rotation of one line segment on to another and they are measured in degrees°.

**Example**

We will need to see if an angle is **acute **(less than 90°), a **right angle** (= 90°), **obtuse **(between 90° and 180°) or **reflex **(more than 180° and less than 360°)

1. AB is turned through 50° to coincide with AC. The angle is labelled **BAC **and is **acute**.

2. A quarter rotation measures 90° and is marked with a square. Angle **BAC **is a **right angle**.

3. A half rotation measures 180°.

4. A complete rotation measures 360°.

We will be looking at lots of different angles in this activity. Although you won't have to actually measure them, it might be a good idea to have a go, in order to practise your measuring skills with a protractor!

In the image above, an angle has been measured using a protractor.

One line of the angle has been lined up with the base line on the protractor and the middle of the base line has been placed at the point of the angle.

The second line of the angle has lined up with the red line shown on the image above. If we look carefully at the red line, we can see that it goes through two numbers 115° and 65°.

How do we know which is the correct answer? We look at the size of the angle! The angle in the image is less than 90°, so it is must be the value 65°. This means that it is an acute angle.

Does that make sense?

Let's give it a go!