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