1. Lesson: 3 – 2 Angle Measure
Applied Geometry
Lesson: 3 – 2
Angle Measure
Objective:
Learn to measure, draw, and classify angles.

2. Angles What are angles measured in?
Degrees: A unit of measure used when measuring angles.
How are the following read?

3. Postulate 3-1 Angle Measure Postulate:
For every angle, there is a unique positive number between 0 and 180 called the degree of measure of the angle.

4. More about angles… How do we measure angles?
Protractor: an instrument used to measure angles in degrees.

5. Types of angles Right Acute Obtuse An angle with a degree of 90
An angle whose measure is less than 90
0 < x < 90
Obtuse
An angle whose measure is greater than 90
90 < x < 180

6. Classifying angles Right Acute Obtuse
Classify each angle as right, acute, or obtuse.
Right
Acute
Obtuse

7. Classify Obtuse Acute Acute
Classify the angles as either right, acute, or obtuse.
Obtuse
Acute
Acute

8. Use a protractor to measure
Find the measure of
Start at the one
side and go ‘up’
to the other side
starting at 0.
Or think of it as:
The angle is acute
so the angle is 45
degrees. (not 135)

9. 115 85 65

10. Using a Protractor To measure an angle
Place the vertex of the angle on the ‘dot’ of the protractor
Line up on side of the angle with the line on the protractor
Read the protractor where the other side crosses.

11. Find the measure of the angle.40

12. Find the measure of the angle.

13. Find the measure 45
100
150

14. Postulate 3-2 Protractor Postulate
On a plane, given and a number r between 0 and 180, there is exactly one ray with endpoint A, extending on each side of such that the degree measure of the angle formed is r.

15. Draw and angle
Use a protractor to draw an angle having a measure of 135 degrees.
First draw one side of the angle (ray with an endpoint.)
Place your protractor on the side drawn
Find 135 degrees (big angle) and place a dot at 135
Connect the dot at 135 with the vertex of the angle.

16. Draw an angle
Use a protractor to draw an angle having a measure of 65 degrees.

17. Example
The measure of angle B is Solve for x.
5x – 7 = 138
Check:
5(29) – 7 = 138
145 – 7 = 138
138 = 138
5x = 145
x = 29

18. Example
3x + 10 = 100
3x = 90
x = 30

19. Homework
Pg – 10 all, 12 – 36 Even