Post on 18-Dec-2015
Chapter 4.1Skew, Parallel and
Perpendicular Lines
Objectives: We’ll learn…
• Define the characteristics of skew, parallel and perpendicular lines.
Skew Lines
Skew lines lie in different planes. They are •Not parallel •Not intersecting •Not perpendicular.
Skew lines
Skew lines are noncoplanar lines.
(Noncoplanar lines cannot intersect.)
SKEW LINES• Lines that lie in different planes. They are neither parallel nor intersecting.
SKEW LINES• Lines that lie in different planes. They are neither parallel nor intersecting.
CD and FA are SKEW LINESFA and BD are SKEW LINES
G BAF
E
HD
C
A B
D C
E F
H G
Use the figure to find the following:Use the figure to find the following:
Two pairs ofParallel Lines
Two pairs ofParallel Planes
Two pairs of Skew Lines
GC HD
AB CD Plane AED Plane BCF AD, BF
EH, CGPlane EFG Plane ABC
PARALLEL LINES
• Def: lines that do not intersect; must be coplanar.
• Illustration:
• Notation: l || m AB || CD
lm
A
B
C
D
p. 129
28
A B
C D
Two lines are parallel if they do not intersect.
CDAB
Read as line AB is parallel to line CD.
EX1: Are the lines parallel?
Examples of Parallel Lines
• Hardwood Floor
• Opposite sides of windows, desks, etc.
• Parking slots in parking lot
• Parallel Parking
• Streets: Laramie & LeClaire
Examples of Parallel Lines
• Streets: Belmont & School
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
29
PERPENDICULAR• Lines that intersect to form
right angles.
90° 90°
90°90°
When two lines intersect at right angles,
They are called perpendicular lines.┴
TRICK: 4 right angles are formed, but it shows 1 only. (The other 3 are invisible.)
Ex. of Perpendicular Lines• Window panes• Streets: Belmont and Cicero
Language of Geometry
Parallel lines & Transversal
Angles, Parallel Lines & Transversal
Homework
p. 144,
1-9,
15-17