1. Points, Lines, and Planes
Section 1-2
Points, Lines, and Planes

2. Introduction
This first chapter will give you the necessary definitions to understand geometry
Please remember the conventions given as that will be how you are expected to present a final answer
Do what you can to remember these definitions
That was a hint

3. Definitions Point Naming convention Partner Up A location
Has no size and takes up no space
Shown as a dot or a corner
Usually labeled with a letter
Naming convention
Read as “point A”
Written as ∙A
Partner Up
Give some real life examples of points

4. Definitions Line m Straight connector between two points
Has no thickness
Extends infinitely in both directions
Labeled with at least two points or an italicized, lowercase letter at one end E F m

5. Definitions Naming conventions (previous examples) Partner Up
If given points
Read as “line EF” or “line FE”
Written as or
If given the letter at the end
Written as it’s read; “line m”
Partner Up
Determine your own definition of a line

6. Definitions Plane Naming Conventions Partner Up A surface
Has no thickness
Usually shown as a shaded shape
The most difficult of the three definitions
Naming Conventions
If given a group of points NOT on the same line
Read and written as “plane DEF”
If given a capital letter off by itself
Read and written as “plane P”
Partner Up
Come up with 4 examples of planes

7. Other Definitions Collinear points Coplanar
Two or more points on the same line
Coplanar
Two or more points or lines on the same plane

8. Example What are other ways to name line QT?V W m n
What are other ways to name line QT?
What are other ways to name plane P?
Name a set of three collinear points.
Name a set of four coplanar points.

9. More Definitions Line Segment A measurable piece of a line
Named by it two endpoints, but sometimes by a single capital letter
Read “segment AB”
Written as or A B

10. More Definitions Ray Half a line
One end is fixed, the other goes forever
Named like a line and a segment, but order is important
Read “ray DE”
Written D E

11. More Definitions Opposite Rays
Two rays that form a line with their shared endpoint
Shown as a line with a third point in the middle
Name the rays, not the line

12. Example 2 Identify the segments in the figure (6 answers)
Identify the rays in the figure (6 answers)
Identify the pair of opposite rays (1 answer)

13. Theories These are called postulates in the book
These postulates are forensics to interpreting geometry
Postulate 1-1
Through any 2 points, there is one line
Postulate 1-2
Two lines intersect at one point
Postulate 1-3
Two planes intersect at one line
Postulate 1-4
Through any 3 noncollinear points there is one plane