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1.4 Angle Measures
Date:
Goals:
• Identify Angle Parts
• Measure and classify angles
Ray:
How to name:
Diagram:
Angle:
How to name:
Diagram:
Interior of an Angle:
Exterior of an Angle:
Example 1: Naming Angles
For each of the following give two names for 1 , then name the sides and vertex.
A.
B.
C.
A
S
A
2
B
1
1
Q
B
C
R
C
Name:
Name:
Name:
Vertex:
Vertex:
Vertex:
Sides:
Sides:
Sides:
Angle measure:
How to read a protractor:
D
1
Angle classifications:
Acute Angle
Right Angle
Obtuse Angle
Straight Angle
Example 2: Classifying an Angle
Classify each angle below based on its measure.
A.
L
B.
A
N
C.
W
F
N
B
C
Congruent Angles:
Example 3: Using Congruent Angles
Use the diagram to the right to answer the following questions.
A. PMJ  ________
B. If mKJL  115 , then what other angle has the same measure?
C. Name two angles that are marked as congruent.
D. Name two angles you think may be congruent. Explain.
B
A
Constructing Congruent Anlges:
Example 4: Constructing a copy of an angle
Use a compass to construct a copy of each angle below.
A.
C
B.
R
A
B
N
G
Angle Bisectors:
Example 5: Using Angle Bisectors
Find the measure of the specified angle in the diagrams below given BD bisects ABC .
A.
C
B
55
B.
C. C
A
D
144
A
D
B
D
B
C
A
mABD 
mABD 
mABD 
mABC 
mDBC 
mDBC 
Example 6: Using Angle Bisectors to Find the Value of Variables
Find the measure of the specified angle in the diagrams below given MG bisects LMN .
B. mLMN  122 and mNMG   9 x  2  
N
M
L
A.
M
5x  2 
 7 x  8 
G
N
L
x=
x=
mLMN 
mLMG 
G
Constructing Angle Bisectors:
Example 7: Construct an Angle Bisector
Construct the angle bisector for each diagram below.
A.
B.