1. Angle
Measurements

2. Degrees: Measuring Angles
We measure the size of an angle using degrees.
Example: Here are some examples of angles and
their degree measurements.

3. Protractor
A device used to measure angles.

4. Acute Angles
An acute angle is an angle measuring between 0 and 90 degrees.
Example:
                                                               

5. Obtuse Angles Example:
An obtuse angle is an angle measuring between 90 and 180 degrees.
Example:
                                                                 

6. Right Angles
A right angle is an angle measuring 90 degrees.
Examples:
                                      

7. These two angles are complementary.
Complementary Angles
Two angles are called complementary angles if the
sum of their degree measurements equals 90 degrees.
Example:
These two angles are complementary.
                                                      
                        

8. These two angles can be "pasted" together to form a right angle!
                        

9. These two angles are supplementary.
Supplementary Angles
Two angles are called supplementary angles if the sum
of their degree measurements equals 180 degrees.
Example:
These two angles are supplementary.
                                                                      

10. These two angles can be "pasted" together to form a straight line!
                                                

11. Vertical Angles
For any two lines that meet, such as in the diagram below,
angle AEB and angle DEC are called vertical angles.
Angle BEC and angle AED are also vertical angles.
Vertical angles have the same degree measurement.                                    
110 70 70
110

12. Review State whether the following are acute, right, or obtuse. 1. 3.5.
acute
obtuse
right 2. 4. ?
acute
obtuse ?

13. Complementary and Supplementary
Find the missing angle.
1. Two angles are complementary. One measures 65 degrees.
2. Two angles are supplementary. One measures 140 degrees.
Answer : 25
Answer : 40

14. Complementary and Supplementary
Find the missing angle. You do not have a protractor.
Use the clues in the pictures. 2. 1. x x 55
165
X=35
X=15

15. Vertical Angles Find the missing angle. You do not have a protractor.
Use the clues in the pictures.
X=58 x 58

16. More drawings F E 20 90 70 D G C 70 90 J 20 H

17. Final Drawing B C 68 60 52 A G D 60 52 68 F E