Transcript 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!!!