1. Transparency 2 Review: Lesson 1-3 Mini-Quiz

2. Class Greeting

3. Objective: The students will learn how to measure angles and how to classify them according to the angle.

4. Chapter 1 – Lesson 4 Angle Measure

5. Vocabulary Degree The unit used to measure angles is the degree One degree is 1/360 th of a circle

6. Vocabulary Ray A ray is part of a line. It has one endpoint and extends forever in one direction. PQ

7. Naming Rays The name of a ray shows the endpoint first and then any other point on the ray This ray is PQ (not QP!) P Q

8. Angles an angle is formed by two non-collinear rays with the same endpoint the rays are called the sides of the angle the endpoint of the rays is the vertex of the angle

9. Angles

10. Opposite Rays A point on a line is the endpoint of two rays on that line called opposite rays Here the opposite rays are QP and QR P Q R Two rays with a common endpoint that form a 180 degree angle are called Opposite Rays. A 180 degree angle is called a Straight Angle.

11. Angles Divide the Plane An angle in a plane divides it into 3 parts: –Points on the angle –Points in the interior of the angle –Points in the exterior of the angle Points A,D & E are on the angle Points C & B are in the interior of the angle Points F & G are in the exterior of the angle

12. Example 4-1a Name all angles that have B as a vertex. Answer:  5,  6,  7, and  ABG

13. Example 4-1b Name the sides of  5. Answer: and or are the sides of  5.

14. Example 4-1c Write another name for  6. Answer:  EBD,  FBD,  DBF, and  DBE are other names for  6.

15. Classifying Angles An angle with measure = 90  is called a right angle

16. Classifying Angles An angle with measure < 90  is called an acute angle

17. Classifying Angles An angle with 180  > measure > 90  is called an obtuse angle

18. Example 4-2a Measure  TYV and classify it as right, acute, or obtuse.  TYV is marked with a right angle symbol, so measuring is not necessary. Answer: is a right angle.

19. Example 4-2b Measure  WYT and classify it as right, acute, or obtuse. is an obtuse angle. Answer: = > is an obtuse angle.

20. Example 4-2c Measure  TYU and classify it as right, acute, or obtuse. Use a protractor to find that m Answer: is an acute angle.

21. Lesson Summary: Objective: The students will learn how to measure angles and how to classify them according to the angle.

22. Preview of the Next Lesson: Objective: The students will learn the Angle Addition Postulate and about different types of angle pairs.

23. Homework Geometry 1-4