8'3 Similar Polygons

1
8.3 Similar Polygons

• Pg 473

2
Similar polygons

• Similar polygons- 2 polygons that have ?
  corresponding ?s and proportional corresponding
  side lengths.

A
B
X
W
D
Z
Y
C
ABCDWXYZ
3
Trapezoid ABCD Trapezoid WXYZ. List all the
pairs of ? ?s and a statement of proportionality
of the ratios of the corresponding sides
A
B
?A_at_?W ?B_at_?X ?C_at_?Y ?D_at_?Z
C
D
W
X
Y
Z
4
Exampledecide whether the ?s are .
X
Yes, because all corresponding ?s are ? and there
is a ratio of 13 between all pairs of
corresponding sides.
)
12
A
)
__
4
36
Z
__
__
12
C
__
21
7
))
))
Y
B
5
Example cont.
M
P
10.5
Not because not all the corresponding ?s are _at_
)
4
12
L
18
Q
9
12
R
(
N
6
Scale Factor

• Scale factor- the ratio of the lengths of 2
  corresponding sides of polygons.

enlargement
painting
The 2 pics are , what is the scale factor b/t
the 2?
42in
12in
__
__
__
36in
__
126in
7
Example cont.What would the ratios of the
perimeters be?

• 2(12)2(36)96
• 2(42)2(126)336

8
Thm 8.1

• If 2 polygons are then the ratio of their
  perimeters is to the ratio of their
  corresponding lengths

Ratio of perimeters scale factor
9
Exampleparallelogram ABCD parallelogram GBEF.
Find the value of y and the ratio of the
perimeters.
B
E
C
12
G
F
Y
15
15y288
Ratio of Perimeters 5/8
y19.2
A
D
24
10
Assignment