7-2 Similar Polygons

1
7-2Similar Polygons

• Objective
• To identify and apply similar polygons

2
Similar Figures same shape but not necessarily
the same size
Abbreviate is similar to with the symbol .

You can use ratios and proportions to decide
whether two polygons are similar and to find
unknown side lengths of similar figures.
3
Similar Polygons And Corresponding sides
are proportional. Notation ?ABC ?DEF
Corresponding angles are congruent
4
Extended Proportion
When three or more ratios are equal, you can
write an extended proportion
5
Scale Factor
Ratio of corresponding linear measurements of two
similar figures

simplify
The ratio of corresponding sides
6
What are the pairs of congruent angles?
What is the extended proportion for the ratios of
corresponding sides?
You give it a shot.
7
Are the polygons similar? If so, write a
similarity statement and give the scale factor.
Pairs of congruent angles
Compare the ratios of corresponding sides
Corresponding sides are not proportional, so the
polygons are not similar.
8
Similar Polygons corresponding angles are
congruent AND corresponding sides are
proportional
Does the AND matter?
Congruent Angles
Proportional sides
No
Yes
Congruent Angles
Proportional sides
Yes
No
9
Similar Polygon Problems
GivenABCDE JKLMN Find x and y
15
9

x 6
10
x
J
15
N
K
y
15

y 18
10
12
y
9
M
L
10
p. 444 9-19 odd (include all ratios diagrams)