Measuring Angles Geometry Mrs. King Unit 1, Lesson 5
Definition Angle: formed by two rays with a common endpoint (“vertex”). C A B
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
Types of Angles 1. Acute Less than 90° 2. Right Exactly 90° 3. Obtuse Greater than 90°, but less than 180°
Types of Angles 4. Straight Exactly 180° 5. Reflex Greater than 180 but less than 360
Definition Congruent Angles: angles with the same measure
Angle Addition Postulate 1-8: If point B is in the interior of AOC, then m AOB + m BOC = m AOC OC B A
Practice m HAT = 50 and m HAM = 125. What is the m MAT? AH T M
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
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
Angle Pairs 3. Complementary Angles: two angles whose measures have a sum of 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.
Homework Measuring Angles in Student Practice Packet (Page 6, #1-13)