1. Classifying and Measuring
Angles
Lesson 3-1

2. Angles
• An angle is made up of 2 rays with a
common end point.
• Angles are measured in units called
degrees.
Vertex- the
point where the
2 rays meet.

3. Naming Angles
C
B
A
2
You can use the symbol to
name the angle.
ABC or CBA Always use the
vertex as the middle letter.
B Use the vertex only
2 Use a number

4. Types of Angles
Acute Angle
Right Angle
Obtuse Angle Straight Angle
Measure less than 90
Measure exactly 90
Measure between 90 and 180 Measure exactly 180

5. Find the measure of an angle
M
R
P
N
60
85

6. The outer scale
goes from 0 to 180
from left to right.
The inner scale
goes from 0 to 180
from right to left.
Protractor

7. How to measure an angle
Line up the vertex of the angle with
the center of the protractor.
Lay one of the rays of the angle on
the line passing through zero.
If the ray
passes
through this
zero, use the
outer scale.
If the ray
passes
through this
zero, use the
inner scale.

8. •Measure this angle from the inner scale.
•This angle measures 75

9. •Measure this angle from the outer scale.
•This angle measures 100

10. Draw an Angle that measures 60
First draw a ray.
Next lay the
protractor on top
of the ray with the
end point at the
center of the ray.

11. Draw an Angle that measures 60
Then draw the other ray passing it through this
point.
Mark the point on the protractor that you want the
other ray to pass through.

12. Draw an Angle that measures 60

13. Your Turn
• Measure the angles on your worksheet.
• Draw your own angle that measures 45
• Remember to line up the vertex with the
center point.
• If you need to extend the ray so that it
passes through the zero mark.