1. Clickers
Bellwork
Solve for x
3x+5+2x-4=36

2. Bellwork Solution
Solve for x

3. Bellwork Solution
Solve for x

4. Bellwork Solution
Solve for x

5. Measure and Classify Angles
Section 1.4

6. The Concept Today we’re going to discuss the different kinds of angles
We’re also going to talk about adding and bisecting angles

7. Definition
Angle
Object that is created by the connection of two rays at the same endpoints
Consists of two sides and a vertex
Named by three points (of which one is the vertex) or just by the vertex if it is not shared with another angle
Object that is created by the connection of two rays at the same endpoints
Consists of two sides and a vertex
Named by three points (of which one is the vertex) B
Angle
1.4 A C
Indicates angle
Axis of symmetry
Vertex

8. Congruence
Similar to our look at line segments, we have to be aware of the difference in use of the congruence and equals signs

9. Protractor Postulate
The measure of an angle (denoted m) is equal to the absolute value of the difference between the real numbers for the two rays as they cross a protractor
In other words, if you measure an angle with a protractor we can be reasonably certain that it’s correct…

10. Classification There are four kinds of angles Acute Right Obtuse
Measuring less than 90 degrees
Right
Measuring 90 degrees
Obtuse
Measuring larger than 90 degrees and less than 180
Straight
Measuring 180 degrees A C B A C B A C A B C

11. On your own
What kind of angle is shown below?

12. On your own
What kind of angle is shown below?

13. On your own
What kind of angle is shown below?

14. Angle Addition Postulate
If P is in the interior of ∠RST, then the measure of ∠RST is equal to the sum of the measures of ∠RSP and ∠PST. R P S T

15. Example R P 35 S 23 T
58o

16. On your own
What is the measure of angle ABD, if the measure of angle ABC is 102o? B
35o C A D

17. Application
Find if is 72 degrees R P
3x+6 S
2x-9 T

18. Congruency
Two angles that have the same measure are considered congruent
Example 4

19. Homework
1.4
2-38 even, (don’t measure, just classify)

20. Bisector angles
Similar to bisectors of lines, a bisector of an angle is a ray that shares the end point of a given angle that splits the measure of the angle in half R P S T

21. Application
Find if is 32o and SP is a bisector R P S T

22. Most Important Points Definition of angles Classification of angles
Angle addition postulate
Congruent Angles
Bisector angles