1. Chapter 13 L13-1 Notes: Angles

2. Vocabulary Angles have two sides that share a common endpoint called the vertex of the angle.

3. Vocabulary The most common unit of measure for angles is the degree. A circle can be separated into 360 equal-sized parts.

4. Types of Angles right angle exactly 90° acute angle less than 90° obtuse angle greater than 90° straight angle exactly 180°

5. Measure Angles Use a protractor to find the measure of each angle. Then classify each angle as acute, obtuse, right, or straight. 1.

6. Measure Angles Use a protractor to find the measure of each angle. Then classify each angle as acute, obtuse, right, or straight. 2.

7. Pairs of Angles Two angles whose sum is 90º are complementary angles.

8. Pairs of Angles Two angles whose sum is 180º are supplementary angles.

9. Find the Missing Measure

10. Chapter 13 L13-2 Notes: Using Angle Measures

11. Estimating Measures To estimate the measure of an angle, compare it to an angle whose measure you know. 1. Estimate the measure of the angle shown. Compare the given angle to an angle whose measure you know. The angle is a little less than a 90° angle. So, a reasonable estimate is about 80°.

12. On Your Own… Estimate the measure of each angle. 1. 2.

13. Draw an Angle Draw a 74 ⁰ angle. Step 1 Draw one side of the angle. Then mark the vertex and draw an arrow. Step 2 Place the center point of the protractor on the vertex. Align the mark labeled 0 on the protractor with the line. Find 74° on the correct scale and make a pencil mark. Step 3 Use a straightedge to draw the side that connects the vertex and the pencil mark.

14. On Your Own… Use a protractor and a straightedge to draw angles having the following measurements. 1. 68 ⁰ 2. 105 ⁰

15. Chapter 13 L13-3 Notes: Bisectors

16. Vocabulary To bisect something means to separate it into two equal parts. Lines with the same measure are congruent. Two line segments are perpendicular if they meet at right angles.

17. Bisect a Line Segment Draw a line segment measuring 6 inches. Then use a straightedge to bisect the segment. Draw a 120° angle. Then use a straightedge and a protractor to bisect the angle.

18. On Your Own… Draw each line segment or angle having the given measurement. Then use a straightedge and a protractor to bisect the line segment or angle. 1. 3 cm 2. 85º