Transcript Slide 1

9-1 Introduction to Geometry
California
Standards
Preparation for MG2.1 Identify angles
as vertical, adjacent, complementary, or
supplementary and provide descriptions
of these terms.
Holt CA Course 1
9-1 Introduction to Geometry
Vocabulary
point
line
plane
ray
line segment
congruent
Holt CA Course 1
9-1 Introduction to Geometry
A point is an exact
location. It is usually
represented as a dot,
but it has no size at
all.
A line is a straight
path that extends
without end in
opposite directions.
Holt CA Course 1
point A
Use a capital
letter to name
a point.
•A
l
X
Y
XY, YX, or l
Use two points
on the line or a
lowercase letter to
name a line.
9-1 Introduction to Geometry
A plane is a
perfectly flat
surface that
extends infinitely
in all directions.
Holt CA Course 1
Q
S
R
plane QRS
Use three points
in any order, not
on the same line,
to name a plane.
9-1 Introduction to Geometry
Additional Example 1: Identifying Points, Lines,
and Planes
Identify the figures in the diagram.
E
A. three points
D
F
D, E, and F
B. two lines
DE, DF
C. a plane
plane DEF
Holt CA Course 1
Choose any three points.
Choose any two points on
a line to name the line.
Choose any three points,
not on the same line to
name a plane.
9-1 Introduction to Geometry
Check It Out! Example 1
Identify the figures in the diagram.
G
I
A. four points
H
F
H, G, I, and F
Choose any four points.
B. two lines
IH, HF
C. a plane
plane IGF
Choose any two points on
a line to name the line.
Choose any three points,
not on the same line to
name a plane.
Holt CA Course 1
9-1 Introduction to Geometry
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.
Holt CA Course 1
G
L
H
M
GH
Name the endpoint
first when naming
a ray.
LM or ML
Use the endpoints
to name a line
segment.
9-1 Introduction to Geometry
Additional Example 2: Identifying Line Segments
and Rays
Identify the figures in the diagram.
M
N
O
A. three rays
MN, NM, MO
Name the endpoint of
a ray first.
B. two line segments
Use the endpoints in
any order to name a
segment.
MN, MO
Holt CA Course 1
9-1 Introduction to Geometry
Check It Out! Example 2
Identify the figures in the diagram.
A. three rays
BC, CA, BD
D
C
Name the endpoint of
a ray first.
B
B. three line segments
Use the endpoints in any
BA, CA, BD
order to name a segment.
Holt CA Course 1
A
9-1 Introduction to Geometry
Figures are congruent if they have the same shape
and size. Line segments are congruent if they have
the same length.
You can use tick marks to indicate congruent line
segments. In the illustration below, line segments
AB and BC are congruent.
Holt CA Course 1
9-1 Introduction to Geometry
Additional Example 3: Identifying Congruent Line
Segments
Identify the line segments that are congruent
in the figure.
AB  CD
One tick mark
AC  BD
Two tick marks
BF  DF  EC  AE Three tick marks
Reading Math
The symbol  means “is congruent to.”
Holt CA Course 1
9-1 Introduction to Geometry
Check It Out! Example 3
Identify the line segments that are congruent
in the figure.
A
B
C
D
E
Holt CA Course 1
AB  AC
One tick mark
BC  DE
Two tick marks
BD  CE
Three tick marks