Page 645 - Basic College Mathematics with Early Integers

622 C HAPTE R 9 I GEOMETRY

Naming an Angle
When there is no confusion as to what angle is being named, you may use the
vertex alone.

A
A
D 1 2
4 3 C
B
1
B E
C
Name of B is not all right.
Name of B is all right.
There is no confusion. B means 1. There is confusion. Does B mean
1, 2, 3, or 4?

PRACTICE 1 Example 1 Identify each figure as a line, a ray, a line segment, or an angle.
Identify each figure as a line, a Then name the figure using the given points.
ray, a line segment, or an angle. a. b.
Then name the figure using the F
D
given points. E
a. A b. S C
R c. M d.
P
B
T
N
c. d.
H
O
E V
Solution:
T
F ·
Figure (a) extends indefinitely in two directions. It is line CD or CD.
Figure (b) has two endpoints. It is line segment EF or EF.
Figure (c) has two rays with a common endpoint. It is ∠MNO, ∠ONM, or ∠N.
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Figure (d) is part of a line with one endpoint. It is ray PT or PT.

Work Practice 1

PRACTICE 2 Example 2 List other ways to name ∠y.
Use the figure in Example 2 to
list other ways to name ∠z.
Q

y R
T
z

S
Answers
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1. a. ray; ray AB or AB Solution: Two other ways to name ∠y are ∠QTR and ∠RTQ. We may not use Copyright 2012 Pearson Education, Inc.
b. line segment; line segment RS
or RS the vertex alone to name this angle because three different angles have T as their
·
c. line; line EF or EF vertex.
d. angle; ∠TVH or ∠HVT or ∠V
2. ∠RTS, ∠STR Work Practice 2