Using a Protractor Geometry Lesson

3 A 180 o Protractor Outside scale from 0 o to 180 o going in a clockwise direction. Inside scale from 0 o to 180 o going in an anti-clockwise direction.

12-Jan-164 You need to be able to measure an angle to the nearest degree. To help you do this you should always: 1. Look directly down onto the cross point. 2. Always use the protractor in a horizontal manner as shown below.

Measuring Angles with a Protractor Place the center point of the protractor on the vertex of the angle.

Measuring Angles with a Protractor Read where the top ray crosses the protractor. (Identifying your angle as acute or obtuse will help you know whether to use the top or bottom set of numbers)

Measuring Angles with a Protractor Therefore this angle has a measure of 50°

8 1 2 Measuring Angles with a 180 o Protractor 0 on the outside so use outside scale 0 on the inside so use inside scale 67 o 50 o

9 3 4 Measuring Angles with a 180 o Protractor 0 on the outside so use outside scale 0 on the inside so use inside scale 135 o 120 o

Drawing Angles with a Protractor The first step should be to extend the rays that form the angle using a straight edge or a ruler.

ACTIVITY 1. Using a protractor, draw the following angles with the given measures ° 2. 15° °