Learn to identify angles and parts of
angles.
Course 2
7-2 Angles
Vocabulary
angle
vertex
right angle
acute angle
obtuse angle
straight angle
complementary angles
supplementary angles
Insert Lesson Title Here
Course 2
7-2 Angles
Course 2
7-2 Angles
An angle is formed by two rayswith a common endpoint. The two rays are the sides of the angle. The common endpointis the vertex.
You can name an angle in three ways:
• with the capital letter at the vertex: B,
• with the number inside the angle: 1,
• with three capital letters so that the letterat the vertex is in the middle: ABC or CBA
A
CB
1
Vertex
Course 2
7-2 Angles
Angles are measured in degrees (°). You can
use a protractor to measure an angle.
The measure of XYZ is 122°, or m XYZ = 122°.
Give the measurement of each angle.
Additional Example 1A & 1B: Identifying Angle
Measures
Course 2
7-2 Angles
A. STV
B. XTU
m STV = 55°
m XTU = 25°
Give the measurement of each angle.
Additional Example 1C &1D: Identifying Angle
Measures
Course 2
7-2 Angles
C. WTU
D. STX
m WTU = 40° + 25°
m STX = 155°
m WTU = 65°
m STX = 55° + 60° + 40°
Try This: Example 1
Give the measure of each angle.
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Course 2
7-2 Angles
A. STV
B. XTU
m STV = 35°
m XTU = 40°
35°
55° 50°
40°S
VW
X
U
T
Try This: Example 1 Continued
Give the measure of each angle.
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Course 2
7-2 Angles
C. WTU
D. STX
m WTU = 50° + 40°
m STX = 140°
m WTU = 90°
m STX = 35° + 55° + 50°
35°
55° 50°
40°S
VW
X
U
T
Course 2
7-2 Angles
An angle’s measure determines the type of angle it is.
A right angle is an angle that measures exactly 90°. The
symbol indicates a right angle
An acute angle is an anglethat measures less than 90°
An obtuse angle is an anglethat measures more than 90°but less than 180°
A straight angle is an anglethat measures 180°
Tell whether each angle is acute, right, obtuse or straight.
Additional Example 2: Classifying Angles
Course 2
7-2 Angles
A. B. C.
right angle obtuse angle acute angle
Try This: Example 2
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Course 2
7-2 Angles
Tell whether each angle is acute, right, obtuse, or straight.
A. B. C.
straight angle acute angle obtuse angle
Course 2
7-2 Angles
If the sum of the measures of two angles is90°, then the angles are complementary
angles. If the sum of the measures of twoangles is 180°, then the angles are
supplementary angles.
Use the figure to name the following.
Additional Example 3A: Identifying Complementary
and Supplementary Angles
Course 2
7-2 Angles
A. one pair of complementary angles
Since 30° + 60° = 90°,
m OMP = 30° and m OMR = 60°
OMP and OMR are complementary.
60° 90°
30°
60°
N Q
P
O
R
M
Use the figure to name the following.
Additional Example 3B: Identifying Complementary
and Supplementary Angles
Course 2
7-2 Angles
B. one pair of supplementary angles
m RMO = 60° and m QMO = 90° + 30° = 120°
Since 60° + 120° = 180°,
RMO and QMO are supplementary.
60° 90°
30°
60°
N Q
P
O
R
M
Use the figure to name the following.
Try This: Example 3A
Course 2
7-2 Angles
A. one pair of complementary angles
Since 30° + 60° = 90°,
m OMP = 30° and m NMQ = 60°
OMP and NMQ are complementary.
60° 90°
30°
60°
N Q
P
O
R
M
Use the figure to name the following.
Try This: Example 3B
Course 2
7-2 Angles
B. one pair of supplementary angles
m QMP = 90° and m PMR = 30° + 60° = 90°
Since 90° + 90° = 180°,
QMP and PMR are supplementary.
60° 90°
30°
60°
N Q
P
O
R
M
Lesson Quiz
Give the measure of each angle, and tell whether it is acute, obtuse, right, or straight.
Insert Lesson Title Here
Course 2
7-2 Angles
1. AFB
2. AFC
3. DFC
4. Name a pair of complementary angles.
5. Name a pair of supplementary angles.
90°; right
140°; obtuse
DFC and CFB
Possible answer: EFA and AFB
40°; acute50°
40°
A
B
CD
E F
Homework
7-2 Worksheet