1. Pearson Unit 3 Topic 9: Similarity 9-1: Similar Polygons Pearson Texas Geometry ©2016 Holt Geometry Texas ©2007

2. TEKS Focus:
(7)(B) Apply the Angle-Angle criterion to verify similar triangles and apply the proportionality of the corresponding sides to solve problems.
(1)(A) Apply mathematics to problems arising in everyday life, society, and the workplace.
(1)(F) Analyze mathematical relationships to connect and communicate mathematical ideas.
(1)(G) Display, explain, or justify mathematical ideas and arguments using precise mathematical language in written or oral communication.

3. A figure with the same SHAPE but not necessarily the same SIZE
VOCABULARY:
Vocabulary Word
Definition
Similar Figure
A figure with the same SHAPE but not necessarily the same SIZE
Scale Factor
The RATIO of corresponding linear measurements in similar figures
Proportion
An equation that states 2 ratios are equal

6. If the scale factor of a dilation is greater than 1 (k > 1), it is an enlargement. The scale factor in fraction form is an improper fraction.
If the scale factor is less than 1 (k < 1), it is a reduction. The scale factor in fraction form is a proper fraction.
Helpful Hint
0 < k < 1,

8. Example 1:

9. Example 2: Compare short/short and long/long. 10 = 15 15 20
10 = 15
Rectangle KLMN ~ Rectangle XYZW
18 = 18 = 18 = 12 = 12
All ratios = 2.
Pentagon ABCDE ~ Pentagon RSTUV

10. Example 3:
6 = y
9y = 30
y = 3 1/3

11. Example: 4

12. Example: 5
Length of main span in scale drawing is 6.4 cm.

13. Example: 6
1 = x
50x = 605
x = 12.1 in
No, the paper would need to be over 12 inches tall