Name_________________
Date_______ Period_____
1.2 Points, Lines, and Planes
Essential Question: What are the building blocks of Geometry?

Geometry is a _______________________ that is built on accepted facts, basic terms, and
_______________.

______________________________ are the basic ideas that you can use to build the definitions
of all other figures.

Any term that cannot be defined using only previously defined terms is considered
____________________.

Undefined terms are the foundation for the ______ ___________ of all other terms in
Geometry.
The Three Undefined Terms of Geometry
Term Description
A ______ indicates a location
and has no size
How to Name It
You can represent a point by a
_____ and name it by _________
__________, such as ______.
A ______ is represented by a
You can name a line by any
straight path that extends in two
___________________ on the
opposite directions without end
line, such as _______ (read “line
and has no _____________. A
AB” or ________. Or, you can
line contains infinitely many
use a single, lowercase, italicized
___________.
letter, such as __________.
A ________ is represented by a
You can name a plane by a
flat surface that extends without
capital letter, such as ________,
end and has no thickness. A
or by at least _____________ in
plane contains infinitely many
the plane that do not all lie on
__________.
the same line, such as plane ABC.
Diagram
Name_________________
Date_______ Period_____

Collinear points:

Coplanar points:

Space:
Example 1:
a.) What are two other ways to name plane P?
b.) What are two other ways to name QT?
c.) What are the names of three collinear points?
What are the names of three noncollinear points?
Definition
How to Name It
A _________ is a part of a line
You can name a segment by its
that consists of two endpoints
two ___________, such as
and all points between them
_____, or _______
A ________ is a part of a line
that consists of one endpoint
and all the points of the line on
one side of the endpoint.
_________________ are two
rays that share the same
endpoint and form a line.
You can name a ray by its
endpoint and another point on
the ray, such as _______. The
order of the points indicates the
ray’s ____________.
You can name opposite rays by
their shared endpoint and any
other point on each ray, such as
___________________.
Diagram
Name_________________
Date_______ Period_____
Example 2:
a.)What are the names of the segments in the figure at the right?
b.) What are the names of the rays in the figure?
c.) Which of the rays in part (b) are opposite rays?
Got it?
EF and FE form a line. Are they opposite rays?

A _______________ or ____________ is an accepted statement of fact.

_______________, like undefined terms, are basic building blocks of the logical system of
Geometry.

Postulate 1-1:

Postulate 1-2:

Postulate 1-3:
Example 3: Each surface of the box below represents part of a plane. What is the intersection of plane
ADC and plane BFG?
Name_________________
Date_______ Period_____
Note: When you name a plane using the corners, like in example 3, you must list the points in
consecutive order. For example using the box below, ADCB and ABCD are correct ways to name the top
plane of the box, but ACBD is not.

Postulate 1-4:
Example 4 Use the figure at the right.
a.) What plane contains points N, P, and Q?
b.) What plane contains points J, M, and Q?
Got it? Use the figure to the right.
a.) What are two other names for line XY?
b.) What are the opposite rays?
c.) What is the intersection of the two planes?