1. Objective To identify and apply similar polygons

2. Abbreviate is similar to with the symbol .
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. Notation: ∆ABC ~ ∆DEF And Similar Polygons:
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
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. Does the AND matter? Similar Polygons:
corresponding angles are congruent
AND
corresponding sides are proportional
Does the AND matter?
Congruent Angles
Proportional sides
12 cm
18 cm
10 cm
Yes No
Congruent Angles
Proportional sides
12 cm
18 cm
500
1300 No
Yes

9. Similar Polygon Problems
Given: ABCDE ~ JKLMN
Find x and y A B C D E 10 12 x 15 9 =
x = 6 10 J x 15 N K y 15 =
y = 18 10 12 y 9 M L

10. p. 444: 9-19 odd (include all ratios & diagrams)