Learn to identify and describe geometric figures'

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Learn to identify and describe geometric figures.
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Vocabulary
point line ray line segment plane congruent
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A point is an exact location in space. It is
usually represented as a dot, but it has no size
at all
point A Use a capital letter to name a point.
A
A line is a straight path that extends without
end in opposite directions.
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A ray is a part of a line. It has one endpoint
and extends without end in one direction.
A line segment is part of a line. or a ray that
extends from one endpoint to another.
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A plane is a perfectly flat surface that
extends infinitely in all directions.
plane QRS Use three points in any order, not on
the same line, to name a plane.
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Additional Example 1 Identifying Points, Lines,
and Planes
Identify the figures in the diagram.
D
E
F
A. three points
D, E, and F
Choose any two points on a line to name the line.
B. two lines
DE, DF
Choose any three points, not on the same line, in
any order.
C. a plane
plane DEF
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Try This Example 1
Identify the figures in the diagram.
G
H
I
F
A. four points
H, G, I, and F
Choose any two points on a line to name the line.
B. two lines
IH, HF
Choose any three points, not on the same line, in
any order.
C. a plane
plane IGF
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Additional Example 2 Identifying Line Segments
and Rays
Identify the figures in the diagram.
M
N
O
A. three rays
Name the endpoint of a ray first.
MN, NM, MO
B. two line segments
Use the endpoints in any order to name a segment.
MN, MO
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Try This Example 2
Identify the figures in the diagram.
D
C
A. three rays
Name the endpoint of a ray first.
A
B
BC, CA, BD
B. three line segments
Use the endpoints in any order to name a segment.
BA, CA, BD
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Figures are congruent if they have the same shape
and size. If you place one on top of the other,
they match exactly. Line segments are congruent
if they have the same length. Tick marks are
used to indicate congruent line segments. In the
illustration below, segments that have the same
number of tick marks are congruent. Line segments
AB and BC are congruent (one tick mark), and
line segments MN and OP are congruent (two tick
marks).
B
5 ft
N
O
20 m
20 m
3 ft
3 ft
C
P
M
A
8 ft
16 m
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Additional Example 3 Identifying Congruent Line
Segments
Identify the line segments that are congruent.
One tick mark
Two tick marks
Three tick marks
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Try This Example 3
Identify the line segments that are congruent.
One tick mark
Two tick marks
Three tick marks
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Lesson Quiz
Use geometric notation to identify figures.
B
A
1. lines
C
G
2. plane
F
Possible answer plane ABG
D
E
3. three rays
4. four line segments
5. How many planes, lines, and points are
suggested by the sides, edges, and corners of
an ordinary box?
6 planes, 12 lines, 8 points