Geometry Section 1 2

1
Geometry Section 1 - 2

• Points, Lines, Planes
• and
• Postulates

2
What is a Point?

• A POINT is a undefined term in Geometry.
• It has no size it is just a location.

A
B
A point is represented by a dot and is named by
using a CAPITAL letter.
3
What is a LINE?
A LINE is a set of points that extends forever in
two directions.
A
B
C
Name this LINE using any two points on the line
and placing a LINE symbol over the letters.
D
AB
BA
AD
BC
AC
4
Another way to name a line
t

• Lines may also be named using one lower case
  letter.

Line t
5
What is a PLANE?
A plane is a flat surface that extends in all
directions without end.
Like a BIG piece of paper butIt has no
thickness!
6
How we name PLANES

• Planes may be named with a single letter
• plane K

K
Planes may be named with three noncollinear
points plane ABC
B
C
A
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Collinear and Noncollinear
Points that lie on the same line are collinear.
C
B
A
NONCOLLINEAR
8
COPLANAR

• Points that lie on the same plane are called
  COPLANAR

B
C
A
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Postulates

• An excepted statement of fact.
• THE RULES OF THE GAME!

Postulate 1-1 Through any two points there is
exactly one line
t
B
A
10
Postulates Continued

• Postulate 1-2
• If two lines intersect, then they intersect in
  exactly one point.

A
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Postulates Continued

• Postulate 1-3
• If two planes intersect, then they intersect in
  a line.

Postulate 1-4 Through any three noncollinear
points there is exactly one plane.
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END SECTION 1.2
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What are PARALLEL LINES?

• Parallel Lines are coplanar lines that will never
  intersect.

Check out these lines!
These lines are PARALLEL LINES!
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What are PARALLEL Planes?

• Parallel Planes are two or more planes that will
  never meet!

P.S. Dont forgetthese planes really extend
FOREVER in every direction!
h
k
Name at least two planes in our room that are
PARALLEL!
t
15
What are SKEW Lines?

• Skew lines are two lines in different planes!

Find two lines in our room that are SKEW!
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