1‐2:Points,Lines
andPlanes
UndefinedTerms
Term
Point
Description
Indicates location
Has no size
Line
Plane
Straight path
Extends in opposite directions
Has no thickness
Infinitely many points
Name Diagram
One capital letter
A
Any two points:

AB or

BA
B
l
A
One lowercase letter:
l
One uppercase Flat surface
Extends without end letter: P
Three points not Has no thickness
Infinitely many lines on same line:
P
A
B
C
ABC
1
TypesofPoints
• Collinear:
• Two or more points that lie on the same line
A
B
C
• Coplanar:
• Three or more points that lie on the same plane
• Lines on the same plane are coplanar
A
C
D
B
• Space:
• Set of all points in three dimensions.
Example1:
B
C
m
E
A
D
Q
F

a. What are two other ways name
AB ?

line l or BA
b. What are two ways to name plane Q?
plane AEC
plane ADC
c. What are the names of three collinear points?
points A, E, D
points A, F, B
d. What are the names of four coplanar points?
points A, E, C
Complete Got It? #1 p.12
points A, E, B

a. RQ b. plane RVS c. N, Q, T
2
DefinedTerms
Term
Description
Segment Part of a line
Name Two endpoints:
Two endpoints and AB or
all points between
Ray
Part of a line
One endpoint and all points on the line on one side of endpoint
Diagram
A
B
BA
Endpoint and any point on the A
ray: 
B
C
AB
Opposite Two rays that share Shared endpoint the same endpoint and any other Ray
point on each Form a line
ray:  
CA CB
A
C
B
Example2:
P
N
M
a. What are the names of the segments in the figure?
MN , NP, MP
b. What are the names of the rays in the figure?
     
MP, NP, MN , PN , NM , PM
c. Which of the rays in part(b) are opposite rays?


NP and NM
Complete Got It? #2 p.13
3
Postulates(statementsassumedtobetrue)
• Postulate 1‐1
• Through any two points there is exactly one line.
A
B
• Postulate 1‐2
• If two distinct lines intersect, then they intersect in exactly one point.
D
A
C
• Postulate 1‐3
G
B
• If two distinct planes intersect, then they intersect in exactly one line.
Example3:
D
A
C
B
H
G
E
F
AG
CG
a. What is the intersection of and ? G
AG
b. What is the intersection of plane ABCD and ?
A
c. What is the intersection of plane ABGH and plane DCHG?

HG
Complete Got It? #3 p.14
a. plane BFE b. Two planes intersect in one line, so you need two common points to name the common line.
4
Postulate
• Postulate 1‐4
• Through any three noncollinear points there is exactly one plane.
A
C
D
B
Example4:Eachsurfaceoftheboxrepresentspartofa
D
C
plane
A
B
H
G
E
F
a. Which plane contains points A, B and C? plane ABCD
b. Which plane contains points E, H and C?
plane EHCB
Complete Got It? #4 p.15

a. plane LMNP b. JM
5
Homework:P.16‐17,#’s8‐22,40‐45
6