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7-2 Angles
Warm Up
Problem of the Day
Lesson Presentation
Course 2
7-2 Angles
Warm Up
Draw each figure.
1. line segment
2. line
3. ray
4. plane
Course 2
7-2 Angles
Problem of the Day
What is the measure of the smaller
angle between the hour hand and the
minute hand on a clock at eight o’clock?
120°
Course 2
7-2 Angles
Learn to identify angles and parts of
angles.
Course 2
7-2 Angles
Insert Lesson Title Here
Vocabulary
angle
vertex
right angle
acute angle
obtuse angle
straight angle
complementary angles
supplementary angles
Course 2
7-2 Angles
An angle is formed by two rays
with a common endpoint. The
two rays are the sides of the
angle. The common endpoint is
is the vertex.
A
Vertex
1
B
C
You can name an angle in three ways:
• with the capital letter at the vertex:
• with the number inside the angle:
B,
1,
• with three capital letters so that the letter
CBA
at the vertex is in the middle:
ABC or
Course 2
7-2 Angles
Angles are measured in degrees (°). You can
use a protractor to measure an angle.
The measure of
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XYZ is 122°, or m
XYZ = 122°.
7-2 Angles
Additional Example 1A & 1B: Identifying Angle
Measures
Give the measurement of each angle.
A. STV
m STV = 55°
B.
Course 2
XTU
m XTU = 25°
7-2 Angles
Additional Example 1C &1D: Identifying Angle
Measures
Give the measurement of each angle.
C.
WTU
m WTU = 40° + 25°
m
WTU = 65°
D. STX
m STX = 55° + 60° + 40°
m
Course 2
STX = 155°
7-2 Insert
AnglesLesson Title Here
Try This: Example 1
Give the measure of each angle.
A. STV
m STV = 35°
B.
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XTU
m XTU = 40°
W
V
S
55° 50°
35°
40°
T
X
U
7-2 Insert
AnglesLesson Title Here
Try This: Example 1 Continued
Give the measure of each angle.
C.
WTU
m WTU = 50° + 40°
m
WTU = 90°
W
V
S
D. STX
m STX = 35° + 55° + 50°
m
Course 2
STX = 140°
55° 50°
35°
40°
T
X
U
7-2 Angles
An angle’s measure determines the type of
angle it is.
A right angle is an angle that
that measures exactly 90°. The
symbol indicates a right angle
An acute angle is an angle
that measures less than 90°
An obtuse angle is an angle
that measures more than 90°
but less than180°
A straight angle is an angle
that measures 180°
Course 2
7-2 Angles
Additional Example 2: Classifying Angles
Tell whether each angle is acute, right, obtuse
or straight.
A.
B.
right angle
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obtuse angle
C.
acute angle
7-2 Insert
AnglesLesson Title Here
Try This: Example 2
Tell whether each angle is acute, right,
obtuse, or straight.
B.
C.
A.
straight angle
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acute angle
obtuse angle
7-2 Angles
If the sum of the measures of two angles is
90°, then the angles are complementary
angles. If the sum of the measures of two
angles is 180°, then the angles are
supplementary angles.
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7-2 Angles
Additional Example 3A: Identifying Complementary
and Supplementary Angles
Use the figure to name the following.
A. one pair of complementary angles
m OMP = 30° and m OMR = 60°
Since 30° + 60° = 90°,
OMP and
OMR are complementary.
N
Q
60° 90°
M
R
Course 2
P
30°
O
60°
7-2 Angles
Additional Example 3B: Identifying Complementary
and Supplementary Angles
Use the figure to name the following.
B. one pair of supplementary angles
m RMO = 60° and
N
Q
60° 90°
m QMO = 90° + 30° = 120°
Since 60° + 120° = 180°,
RMO and QMO are supplementary.
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M
R
P
30°
O
60°
7-2 Angles
Try This: Example 3A
Use the figure to name the following.
A. one pair of complementary angles
m OMP = 30° and m NMQ = 60°
Since 30° + 60° = 90°,
OMP and
NMQ are complementary.
N
Q
60° 90°
M
R
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P
30°
O
60°
7-2 Angles
Try This: Example 3B
Use the figure to name the following.
B. one pair of supplementary angles
m QMP = 90° and
N
Q
60° 90°
m PMR = 30° + 60° = 90°
Since 90° + 90° = 180°,
QMP and PMR are supplementary.
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M
R
P
30°
O
60°
7-2 Angles
Insert Lesson Title Here
Lesson Quiz
Give the measure of each angle, and tell
whether it is acute, obtuse, right, or straight.
1.
2.
3.
AFB
90°; right
AFC
140°; obtuse
DFC
40°; acute
A
E
F
D 40°
4. Name a pair of complementary angles.
DFC and CFB
5. Name a pair of supplementary angles.
Possible answer:
EFA and AFB
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B
50°
C