1. Measuring Angles Geometry Mrs. King Unit 1, Lesson 5

2. Definition Angle: formed by two rays with a common endpoint (“vertex”). C A B

3. Name the angle below in four ways. *The name can be the vertex of the angle: G. The name can be a point on one side, the vertex, and a point on the other side of the angle: AGC, CGA. The name can be the number inside of the angle: 3. Practice

4. Types of Angles 1. Acute Less than 90° 2. Right Exactly 90° 3. Obtuse Greater than 90°, but less than 180°

5. Types of Angles 4. Straight Exactly 180° 5. Reflex Greater than 180  but less than 360 

6. Definition Congruent Angles: angles with the same measure

7. Angle Addition Postulate 1-8: If point B is in the interior of  AOC, then m  AOB + m  BOC = m  AOC OC B A

8. Practice m  HAT = 50 and m  HAM = 125. What is the m  MAT? AH T M

9. m 1 + m 2 = m ABC 42 + m 2 = 88 m 2 = 46 Suppose that m 1 = 42 and m ABC = 88. Find m 2. Practice

10. Angle Pairs 1. Vertical Angles: two angles whose sides are opposite rays  1 and  3 are vertical angles, and  2 and  4 are vertical angles. 2. Adjacent Angles: two coplanar angles with a common side, a common vertex, and no common interior points.  1 and  2 are adjacent angles

11. Angle Pairs 3. Complementary Angles: two angles whose measures have a sum of 90. 4. Supplementary Angles: Two angles whose measures have a sum of 180. In the diagram, these angles are supplementary:  1 and  2,  2 and  3,  3 and  4, and  4 and  1.

12. Homework Measuring Angles in Student Practice Packet (Page 6, #1-13)