Measuring angles using a half circular cut-out
Group Activity 5
In pairs:
- Draw half a circle.
- Divide it into 18 equal sectors. Each sector is 10º.
- Cut out half of the circle.
- Use the half circle to measure angles.
Example 3
Use the half disc to measure the angles shown.
Exercise E
Measuring angles using a protractor
Angles are measured using a protractor. A protractor is divided into 180 small units. Each unit is one degree (1º). A protractor has an inner and outer scale as shown.
A protactor
Group Activity 6
Use a protractor to measure the angle shown.
In pairs:
- Place the centre of the protractor on G.
- Place the protractor such that the line through 0º and 180º lies on GH.
- Read the angle on which GF lies.
Note: If line GF does not cut the outer numbers, extend the line. - Discuss the results and share with other groups.
Example 4
Use a protractor to measure the angle shown.
Exercise F
Digital Time
Angles