Points, Lines, and Planes

1
Lesson 1-1

• Points, Lines, and Planes

2
Building Blocks of Geometry

• Definition
• The three building blocks of geometry are points,
  lines, and planes.

3
Points
Definition It is the most basic building block
of geometry. It has no size. It has only
location.
B
A
How to sketch a dot
C
How to label
A
Use capital printed letters.
Never label two points with the same name
(in the same sketch).
4
Lines
Definition It is straight continuous
arrangement of infinitely many points. It has
infinite length but no thickness. It extends
forever in two directions.
n
NEVER
?
How to sketch
?
?

• must have arrows
• at both ends

?
?
?
How to label
Possible Names
(Two methods)
1- small script letter
2- any two points on the line
5
Planes
horizontal edges
Definition It has length and width but no
thickness. It is a flat surface that extends
infinitely along its length and width.
M
P
How to sketch
N
horizontal
vertical
other
vertical edges
How to label
(Two methods)
1- capital script letter
2- any three points on the plane
6
Collinear Points
Collinear points are points that lie on the same
line. (The line does not have to be visible.)
Definition
non-collinear
collinear
7
Coplanar
Definition Points on the same plane
Example

• Points D, E, and F are coplanar.

D
F
E
8
Line Segment
Consists of two endpoints and all points between
Definition
How to sketch
How to name
9
Congruent Segments
Definition
Congruent segments can be marked with . . .
Correct notation
Incorrect notation
10
Midpoint
A point that divides a segment into two congruent
segments.
Definition
11
Segment Bisector
Any object that divides a segment into two
congruent parts which is the bisector of the
segment.
Definition
12
Ray
Definition
A ray begins at a point and extends infinitely in
one direction.
How to sketch
How to name