Lesson 1-1 Point, Line, Plane
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Geometry
Lesson 1-1 Point, Line, Plane
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
Points do not have actual size.

How to Sketch:
Using dots

A
B
C
A
How to label:
Use capital letters
Never name two points with the same letter
(in the same sketch).
Lesson 1-1 Point, Line, Plane
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•
A is a measure of length, width, or
height.
length
Lesson 1-1 Point, Line, Plane
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Lines extend indefinitely and have no thickness or
width.
 A line is 1 dimensional (length)
 How to sketch : using arrows at both ends.

n
A
B
How to name: 2 ways
C
(1) small script letter – line n
AB , BC, AC , BA, CA, CB
(2) any two points on the line  Never name a line using three points –


Symbol
ABC
Lesson 1-1 Point, Line, Plane
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

Collinear points are points that lie on the same line. (The line does
not have to be visible.)
A point lies on the line if the coordinates of the point satisfy the
equation of the line.
Ex: To find if A (1, 0) is collinear with
A
B
the points on the line y = -3x + 3.
Substitute x = 1 and y = 0 in the equation.
Collinear
0 = -3 (1) + 3
0 = -3 + 3
0=0
The point A satisfies the equation, therefore the point is collinear
with the points on the line.
Lesson 1-1 Point, Line, Plane
C
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Points that do NOT lie on the
same line
 Points A, B, &
A
B
D
C
C are…
Non collinear
C
A
E
Lesson 1-1 Point, Line, Plane
B
Non collinear
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A plane is a flat surface that extends indefinitely in all directions.
 How to sketch: Use a parallelogram (four sided figure)
 How to name: 2 ways
(1) Capital script letter – Plane M

(2) Any 3 non collinear points in the plane - Plane: ABC/ ACB / BAC /
BCA / CAB / CBA
A
B
M
C
Horizontal Plane
Vertical Plane
Lesson 1-1 Point, Line, Plane
Other
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A
D
B
C
E
H
Plane ABCD
Plane EFGH
F
G
Plane BCGF
Plane ADHE
Plane ABFE
Plane CDHG
Etc.
Lesson 1-1 Point, Line, Plane
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Any three non collinear points determine a plane!
A
D
B
Plane AFGD
Plane ACGE
C
Plane ACH
E
H
F
G
Plane AGF
Plane BDG
Etc.
Lesson 1-1 Point, Line, Plane
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Coplanar objects (points, lines, etc.) are objects that lie on
the same plane. The plane does not have to be visible.
A
D
B
C
E
H
F
G
Are the following points coplanar?
A, B, C ?
A, B, C, F ?
H, G, F, E ?
E, H, C, B ?
A, G, F ?
C, B, F, H ?
Lesson 1-1 Point, Line, Plane
Yes
No
Yes
Yes
Yes
No
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The intersection of two figures is the set of points that are
common in both figures.
The intersection of two lines is a point.
m
Line m and line n intersect at point P.
P
n
Lesson 1-1 Point, Line, Plane
Continued…….
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(1) Line passes through plane – intersection is a point.
(2) Line lies on the plane - intersection is a line.
(3) Line is parallel to the plane - no common points.
Lesson 1-1 Point, Line, Plane
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B
AB
P
A
R
Plane P and Plane R intersect at the line
Lesson 1-1 Point, Line, Plane
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•
Is straight and made up of points
•
Has a definite beginning and definite
end
Name a line segment by using the
endpoints only
You will always use two letters to
name a segment
Symbol
•
•
•
Name of these segments:
Name of segment
from -2 to 0.
Lesson 1-1 Point, Line, Plane
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





Is straight and made up of points
Has a beginning but no end
Starting pt. of a ray is called the endpoint
Name a ray by using the endpt. 1st and another
point on the ray
You will always use two letters to name a ray
Symbol
Names of these rays:
Lesson 1-1 Point, Line, Plane
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