1. Points, Lines and Planes
Building Blocks of Geometry
Section 1.2

2. named by capital letter
POINT
has no size
represented by a dot
named by capital letter
P (yay I’m a point!)

3. LINE
Has no thickness
Extends in both directions forever!
named a variety of ways:

4. PLANE An imaginary flat surface that stretches forever
Has no thickness
Drawn as a 4-sided figure
Labeled with a capital letter

5. Can you think of some everyday objects that could model a
POINT?
LINE?
PLANE?

6. But wait a second….. SPACE We Don’t live in FLATLAND (a plane)
We live in a world of 3 dimensions
And we call this set of all points….
SPACE

7. So think of….. Space as 3 dimensions (3-d) A Plane as 2 dimensions
A Line as 1 dimension
And the poor lonely point as…
Yes, zero dimensions.

8. More Vocabulary (yeah!)
When points lie on the same line they are said to be
COLLINEAR
And if they don’t, well then they’re
NON-COLLINEAR

9. Even More Vocabulary
When points lie on the same plane they are said to be
COPLANAR
And if they don’t, well then they’re
NON-COPLANAR

10. ACTIVITY Find four points in this room that are coplanar
Find four points in this room that are non-coplanar

11. INTERSECTION The intersection of two figures is where they “cross”.
What is the intersection of two different lines?
What is the intersection of two different planes?
Are there exceptions to your rules above?

12. Conclusions Two different lines intersect at a Or else they are
point
Or else they are
Parallel (or skew)
Two different planes intersect at a
line
parallel