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Name Class Date
Practice (continued) Form G
Properties of Parallel Lines
13. Write a two-column proof.
Given: a
b, x
y
Prove:
is supplementary to
.
Statements Reasons
14. Visualization One pair of parallel lines intersect a second pair of parallel
lines. One of the angles of intersection has a measure of 60. How can you
determine the measure of the four interior angles? Draw a sketch to support
your answer.
15. Error Analysis Which solution for the gure at the
right is incorrect? Explain.
16. A zip line consists of a pulley attached to a cable
that is strung at an angle between two objects.
In the zip line at the right, one end of the cable
is attached to a tree. e other end is attached
to a post parallel to the tree. What is the measure
of
? What type of angle pair do
and the
given angle represent?
a
b
x y
1 2
3
4
5 6
7
8
9
10
11
12
13
14
15
16
q r
e
f
(2
x
40)
(
x
10)
1
115
1)
;
2)
3)
4)
and
are suppl.
5)
6)
7)
and
are suppl.
1) Given
2) Alt. ext. angles are
.
3) Definition of congruent
4) Same-side int.
are suppl.
5) Def. of suppl.
6) Substitution property
7) Def. of suppl.
Answers may vary. Sample:
Answers may vary. Sample: If the measure of the
given angle is 60, then
and
are both 120 because
same-side interior angles are supplementary. Because
and
are also supplementary,
is 60.
Second solution; the angles are alternate
interior angles, which means they are
congruent.
A
C
D
60
; alternate interior angles