1. Measuring and Naming Angles
Lesson 1
Lines & Angles
Measuring and Naming Angles

2. Warm-Up Solve for x. x + 9 = 90 Solve for x. 10x = 90
Draw two lines that are parallel.
Draw two lines that intersect at about 90º.

3. Measuring and Naming Angles
Target: Measure, name and draw angles.

4. Vocabulary Angle: A figure formed by two rays with a common endpoint.
Ray: Part of a line that has one endpoint and extends forever in
one direction.
Vertex: The common endpoint of two rays that form an angle.
Adjacent Angles: Two angles that share a ray.
Protractor: A tool used to measure angles.
Degrees: A unit used to measure angles.

5. Example 1 Give 4 different names for the given angle.  PAL  LAP  A
 1

6. Example 2 Is W another name for  NWE? Explain.
No, it is not clear whether  W refers to  NWE,
 SWE or  NWS.

7. Example 3 Identify at least one additional name for each angle. a.  1
 TGE or  EGT
b.  TGI
 2 or  IGT
c.  RGE
 EGR or  3

8. Using a Protractor to Measure Angles
Place the bottom edge of the protractor on one ray of the angle.
Slide the protractor so the center of the bottom edge is on the vertex of the angle.
Begin at 0° and use your finger to curve around the protractor until your finger is lined up with the other ray of the angle. The number that the ray lines up with is the measure of the angle.

9. Example 4
Use a protractor to measure each angle.

10. Exit Problems Draw an angle that measures 40°.
Name the angle below three ways.

11. Communication Prompt
You have a friend who does not know how to use a protractor. How would you explain to them how to use it to measure an angle?