1. 3.1 Relationships between lines

2. Vocabulary
Parallel Lines- two lines that lie in the same plane and do not intersect
Illustration:
Notation: l ||m AB || CD A B C D l m

3. Examples of parallel lines
Hardwood Floor
Opposite sides of windows, desks, etc.
Parking slots in parking lot

4. Vocabulary
Perpendicular- two lines who are in the same plane that intersect at a 90° angle
Illustration: Notation: m  n m n

5. Examples of perpendicular lines
Streets: Franklin Ave and Centre Street

6. Vocabulary
Skew Lines- Two lines who are in different planes and never intersect. Skew lines are NOT parallel.
Illustration- Notation: AE and CD are skew

7. Examples of skew lines

8. Skew lines continued Are the following lines skew…? No, they are ||
1. AE and FB?
No, they are ||
2. FB and CG?
No, they are ||
3. AE and BD?
Yes, they are skew

9. Vocabulary Parallel Planes- planes that do not intersect
Plane AEB || Plane CGH

10. Example 1
Fill in the blank with ∥ or ⊥ ⊥ ∥ ⊥ ∥

11. Example 2 Identify each of the following
a. a pair of parallel segments
BF || EJ
b. a pair of skew segments
BF and DE are skew.
c. a pair of perpendicular segments
BF  FJ
d. a pair of parallel planes
plane FJH || plane BCD

12. Example 3 Identify each of the following
I. a pair of parallel segments
EH || FG
J. a pair of skew segments
BF and EH
K. a pair of perpendicular segments
CG  GH
L. a pair of parallel planes
Plane ABC || Plane EFG