1. Skew, Parallel and Perpendicular Lines
Chapter 4.1
Skew, Parallel and Perpendicular Lines

2. Objectives: We’ll learn…
Define the characteristics of skew, parallel and perpendicular lines.

3. Skew Lines Skew lines lie in different planes. They are Not parallel
Not intersecting
Not perpendicular.

4. Skew lines Skew lines are noncoplanar lines.
(Noncoplanar lines cannot intersect.)

5. SKEW LINES
Lines that lie in different planes. They are neither parallel nor intersecting.

6. SKEW LINES
Lines that lie in different planes. They are neither parallel nor intersecting.
CD and FA are SKEW LINES
FA and BD are SKEW LINES G B F A H D E C

7. Use the figure to find the following:A B E F D C H G
Two pairs of
Parallel Lines
Two pairs of
Parallel Planes
Two pairs of
Skew Lines

8. PARALLEL LINES 28 Def: lines that do not intersect; must be coplanar.
Illustration:
Notation: l || m AB || CD A B C D l m
p. 129

9. Two lines are parallel if they do not intersect.B C D
Read as line AB is parallel to line CD.
EX1: Are the lines parallel?

10. Examples of Parallel Lines
Hardwood Floor
Opposite sides of windows, desks, etc.
Parking slots in parking lot
Parallel Parking
Streets: Laramie & LeClaire

11. Examples of Parallel Lines
Streets: Belmont & School

12. 29
PERPENDICULAR LINES
Def: Lines that intersect to form a right angle.
Illustration:
Notation: m  n
Key Fact: 4 right angles are formed. m n
p. 79

13. PERPENDICULAR Lines that intersect to form right angles. 90° 90° 90°

14. When two lines intersect at right angles,
TRICK: 4 right angles are formed, but it shows 1 only. (The other 3 are invisible.)
They are called perpendicular lines. ┴

15. Ex. of Perpendicular Lines
Window panes
Streets: Belmont and Cicero

16. Language of Geometry

17. Parallel lines & Transversal

18. Angles, Parallel Lines & Transversal

19. Homework
p. 144,
1-9,
15-17