1.1
Points, Lines, and Planes
Today you will
Identify and model points, lines, and planes
Identify intersecting lines and planes
In geometry there are three undefined terms: point, line and plane.
Undefined Terms can only be explained using examples and
descriptions.
We must be in agreement about what each is.
Point: A location; has no size and no shape
Named by a capital letter
Example:
A
point A
Line: made up of points; has no thickness
*There is exactly one line through any 2 points
Named by the letters of 2 points on the line or
a lower case script letter
Example:
line PQ
line QP
line m
PQ
QP
m
Q
P
Plane: flat surface made of points that
extend infinitely in all directions
*There is exactly one plane through any 3 points not
on the same line.
Named by capital script letter or
3 non-collinear points
Z
X
Example: plane K
Y
plane XYZ
plane WYZ
W
K
Collinear Points lie on the same line
Coplanar Points lie on the same plane
The intersection of two lines is
The intersection of two planes is
Definitions or Defined Terms are explained using
undefined terms and/or other defined terms.
Space: A boundless, 3-dimensional set of all points
Space can contain lines and planes
Locus: A set of points that satisfy a particular condition
Example:
Represent the locus of points satisfying the equation
x+4=y
using a table of at least 3 values
x
y
Represent the same locus of points using a graph
E
Examples.
C
B
A
1. Name four coplanar points.
2. Name 3 lines.
3. Name a plane.
D
Tonight's HW:
1.1 # 13-47 odds, 53-54, 58, 61