Lesson 1.4: Angle Measure

Lesson 1.4: Angle Measure Geometry CP Mrs. Mongold New Vocabulary Ray: is a part of a line, it has one endpoint and extends indefinitely in one direction.

A B ** Always name rays with their endpoint first!! Opposite Rays: are two rays that share an

endpoint AND form a straight line! X Y Z

Ray YX and ray YZ are opposite rays Chapter 1 Foldable Flap 4 Note when naming an angle with three letters, the vertex must always be the middle letter!

Example Name all the angles that have B as a vertex Answers Answer: Example

Name a side of angle 5 Answer Ray BG Ray BE Ray BF

Chapter 1 Foldable Flap 4 Classify the angles Congruent Angles An angle bisector is a ray that divides an angle

into two congruent angles Example In the figure, Rays QP and QR are opposite rays, and ray QT bisects angle RQS. S

T R Q P

Example If angle RQT = 6x + 5 and angle SQT = 7x 2 find RQT S T R

Q P Answer 6x + 5 = 7x 2 7=x

RQT = 6(7) + 5 = 42 + 5 = 47 Example Find angle TQS if angle RQS = 22a 11 and angle RQT = 12a - 8

S T R Q P

Answer 22a 11 = 2(12a 8) 22a 11 = 24a 16 5 = 2a a = 2.5 TQS = RQT

= 12(2.5) 8 = 30 8 = 22 How to use a protractor First make sure the numbers are not backwards, then you line up the center of the circle on the bottom of the

protractor with the vertex of the angle This is the hole to be lined up with the vertex Using a protractor

Use the small line through the circle to line up the side of the angle. DO NOT use the bottom of the protractor!! Using a protractor You always start at 0 on the side of the angle you lined up, this is

how you tell to use the inside or outside numbers! We are using the inside numbers here since 0 starts on the right!! Answer The angle measure is approximately 730

Using a protractor continued What is the measure of the ange? Answer 107o we are using the outside numbers because the angles edge is to the left

Summarizing Lesson 1.4 Write a note to the absent student explaining lesson 1.4, be very specific about the things we learned. You may use your

foldable and notes if you would like. Write complete sentences!!!