1. Angles

2. Angles • Angles have two sides that share a common endpoint called a vertex of the angle. • Angles are most commonly measured in degrees – for example 90°, 175° VERTEX ANGLE SIDE

3. Naming an Angle • An angle is named by the letters on the angle. Order IS IMPORTANT!!! • This is angle PQR or RQP • The point or vertex of the angle is always in the middle P Q R

4. Name the angle C CED or DEC E D JLK or KLJ L K J

5. Classifying Angles – 4 types RIGHT ANGLE – an angle that is exactly 90° ACUTE ANGLE – an angle that is less than 90° OBTUSE ANGLE – an angle that is more than 90° STRAIGHT ANGLE – an angle that is exactly 180°

6. D E C 36O 56O 28O B 34O F 26O G A Name an angle within the figure that is an acute angle Name an angle within the figure that is an obtuse angle Name an angle within the figure that is a right angle Name an angle within the figure that is a straight angle

7. Measuring Angles Notice 2 sets of numbers!! • Angles are measured with a protractor

8. When measuring angles, place center of the protractor on the vertex. Make sure one side of the angle crosses 0. See where the other side crosses the protractor. The measure of this angle is 50° Use the TOP set of numbers because the one side that crosses the 0 has the 0 that is on the top.

9. What is the measure of the angle? The angle is 75° Do you use the top set of numbers or the bottom? Notice where the 0 is!

10. You may have to turn the protractor to line up the 0 with one side of the angle. What is the measure of the angle? 129°

11. What is the measure of WST? 155° U V T W S R

12. What is the measure of RSU? 86° U V T W S R