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Do Now 2/22/10
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Take out your HW from last week.
 Text
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p. 285, #1-10 all
Copy HW in your planner.
 Text
p. 291, #8-20 all
 Review “Geometry NJASK7 Prep”
assignment on MySkillsTutor – Quiz Friday
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Be ready to copy POTW #4.
“Basic Geometry Concepts”
Point
position in space
represented by a dot.
A
L
D
Z
K
Plane
a flat surface that extends on
forever in all directions.
How many planes on this figure?
Line segment
part of a line with 2 endpoints
and all the points in between.
D
EF
FE
E
C
CD DC
F
Line
a straight path extending
without end in 2 directions.
R
S
ST
T
RT
RS
Ray
Part of a line that begins
at a point and extends in one
direction without ending.
B
A
A
K
AB
J
K
JK
Congruent
Two line segments are
congruent when they are the
same length.
C
3
CD  EF
EF  3
D
E
F
Angle
Two rays that begin at the
same point.
D
Sides
C
Vertex
E
Naming Angles
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The following angle can be named in three ways:
B
C
A
BAC
CAB
Vertex
A
Objective
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SWBAT identify similar and congruent
figures
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Homework
Text p. 286, #1-10 all
1) M, N, P, R, S
2) MN & RS
3) plane Y and plane Z
4) MN , NP, RS , SR
5) RS , MN , NP
6) N ; mN  85
7) quadrilateral DEFG
8) DE , EF , FG, DG
9) D, E, F , G,
10) D  F , E  G,
DE  FG, EF  DG
Section 6.4 “Similar and Congruent Figures”
Similar Figures
Two figures are SIMILAR FIGURES if they have
the same shape but not necessarily the same
size. The symbol ~ indicates two figures are
similar.
Properties of similar figures:
1). Corresponding angles are congruent
2). Corresponding sides are proportional (equal ratios)
Corresponding angles –
matched angles of two figures
ABC ~ DEF
A  D
C  F
When 2 angles
have the same
measure, they are
marked with the
same symbol.
A
D
F
B  E
E
C
B
Corresponding sides –
matched sides of two figures
ABC ~ DEF
AB
AC BC


DE
EF
DF
D
A
F
E
C
B
Given ABC ~ XYZ, name the corresponding
angles and corresponding sides.
Z
A
X
Y
Angles
C
B
A  X ,
B  Z ,
C  Y
Sides
AB and XY ,
AC and XZ ,
CB and YZ
Given ABC ~ DEF, find the ratio of the
lengths of the corresponding sides.
AC
AB CB


DF
DE
FE
A
16 32 28


20 40 35
32
D
40
20
F
16
C
28
B
35
16 4

20 5
32 4

40 5
28 4

35 5
E
The ratio of the
lengths of the
corresponding
sides is 4/5.
Given ABC ~ DEF, find the ratio of the
lengths of the corresponding sides.
AC
AB CB


DF
DE
FE
A
4
5
3


6 7.5 4.5
5
D
7.5
6
F
4
C
3
B
4.5
5
50 2


7.5 75 3
3
30 2


4.5 45 3
4 2

6 3
E
The ratio of the
lengths of the
corresponding
sides is 2/3.
Congruent Figures
Two figures are CONGRUENT FIGURES if they
have the same shape AND the same size.
Properties of congruent figures:
1). Corresponding angles are congruent
2). Corresponding sides are congruent
Given
ABC  XYZ, find the indicated measure.
Z
A
X
15
45
20
Y
35°
C
B
YX 
CB 
45
15
mZ  90°
mY  35°
mA  55°
Homework
Text p. 291, #8-20 all