How_To_Be_Good_At_Math

238 GEOMETRY •^ USING A PROTRACTOR

Using a protractor

We use a protractor to draw and measure angles accurately.

Some protractors measure angles up to 180°, while others

can measure angles up to 360°.

Drawing angles

A protractor is essential if you need

to draw an angle accurately.

180°

PROTRACTOR

Each small

mark represents

one degree (1°)

360°

PROTRACTOR

PROTRACTOR

TRIANGLE

Mark a point

on the line

Make a

second mark

at 75°

Put the protractor’s centre on the

marked point. Read up from 0°,

and make a second mark at 75°.

Use a ruler and pencil to draw a

line between the two points, then

label the angle.

Here’s how to draw a 75° angle.

Draw a straight line with a pencil

and ruler, and mark a point on it.

Use the inner

scale to

measure angles

anticlockwise

Use the outer scale to

measure angles clockwise

Draw a

Line graphs

between the

two points

0° 75º

Always place the protractor

so its centre is exactly on

the angle’s vertex (point).

238_239_Using_a_protractor.indd 238 29/02/2016 18:05