# Geometry: Understanding Parallel Lines

Contributed by:
This pdf includes the following topics:-
Properties of parallel lines and transversals
Using properties of parallel lines in proofs
1. Opportunity is Today:
missed by most •Homework
people because it is Check
dressed in overalls •3.2 Check Up
and looks like work. •Practice
Thomas Edison
2. Opportunity is Assignment:
• 3.1-3.2 p. 197 #1-
missed by most 14
people because it is
dressed in overalls
and looks like work.
Thomas Edison
3. 3.1 Check Up
Identify the vocabulary term for each pair
of angles represented in the picture.
1. 3 and 6
2. 1 and 8
3. 2 and 6
4. 1 and 6
5. 3 and 5
4. You named angle pairs formed by parallel lines
and transversals.
• Use theorems to determine the relationships
between specific pairs of angles.
• Use algebra to find angle measurements.
5. Content Standards
G.CO.1 Know precise definitions of angle, circle,
perpendicular line, parallel line, and line segment,
based on the undefined notions of point, line, distance
along a line, and distance around a circular arc.
G.CO.9 Prove theorems about lines and angles.
Mathematical Practices
1 Make sense of problems and persevere in solving
3 Construct viable arguments and critique the
reasoning of others.
6. 3.2 Angles and Parallel Lines
1.Properties of parallel lines
and transversals
2.Using properties of parallel
lines in proofs
parallel, transversal,
corresponding, alternate
interior, alternate exterior,
consecutive interior
7. 3.2 Angles and Parallel Lines
If 2 parallel lines are cut by a
transversal,angles
corresponding then: are congruent.
alternate interior angles are congruent.
alternate exterior angles are congruent.
alternate exterior
consecutive interior angles are
supplementary.
consecutive interior
angles 12
4 3
5 6
8 7
8. 3.3 Parallel Lines and
Transversals
If l1|| l2, find x. l1
2x + 4
What type of l2
angles do
you have? 110
x = 53
9. If l1|| l2, find x and y.
l1
y + 20
x = 105
x l2
y = 85 75
10. 3.3 Parallel Lines and Transversals
How many angles in the diagram
have a measure of 100o?
100o
11. Given: l1|| l2 2
3
l3 || l4
Prove: 1 2 1
Statements Reasons
1. Given  ALWAYS
4. Transitive Property of
Congruency.
12. Opportunity is Assignment:
missed by most • 3.2 p. 183 #5, 8, 25, 49
people because it is
dressed in overalls
and looks like work.
Thomas Edison