1. Exploring Similar Polygons
8-3
Exploring Similar Polygons
Objectives:
To identify similar figures.
To solve problems involving similar figures.

2. Vocabulary
Similar Figures ~
Scale Factor

3. Similar Figures Definition of Similar Polygons
Two polygons are similar if an only if their corresponding angles are congruent and the measures of their corresponding sides are proportional.
Same shape, usually a different size.

4. ~ The symbol ~ means “is similar to”. We would write ABCD ~ EFGH
Please note, that as with congruence the order of the letters is important.

5. Scale Factor Definition of Scale Factor
The ratio of the lengths of two corresponding sides of two similar polygons is called the scale factor.
It is extremely important to note the order of the words. It makes a difference in the answer.

6. Scale Factor
The scale factor of quadrilateral ABCD to quadrilateral EFGH is 2.
Pick any two corresponding sides. Let’s use AD and EH. Write as a ratio and reduce if possible. 10:5 reduces to 2:1 and with scale factor we can just call it 2.

7. Scale Factor
The scale factor of quadrilateral EFGH to quadrilateral ABCD is ½.
Let’s use EH and AD. Written as a ratio that is 5:10 which reduces to ½.

8. Example 1 Polygon RSTUV is similar to polygon ABCDE.
Find the scale factor from polygon RSTUV to polygon ABCDE.
Find the values of x and y.

9. 2x - 8 In Class Examples B A Scale factor from B to A = 1:2
Solve for x. The polygons are similar.
Scale factor from B to A = 1:2 B 16 A
2x - 8

10. Homework
8-3 Worksheet