1. Using Similar Figures
Chapter 5
Section 5.5

2. Objective
The students will learn to use the proportions to find missing lengths in similar figures.

3. Vocabulary
Polygon – a closed plane figure formed by three or more line segments that do not cross

4. Key Concept Two polygons are similar polygons if
- corresponding angles have the same measures
-the lengths of the corresponding sides form equivalent ratios
40°
40° 6 12 10 5
50° 4
90°
90°
50° 8

5. Example Write a proportion 𝐴𝐶 𝑂𝐷 = 𝐴𝑇 𝑂𝐺 Substitute 𝑥 50 = 24 30D C
40 cm
32 cm cm G
x cm T
24 cm cm
A O
Write a proportion 𝐴𝐶 𝑂𝐷 = 𝐴𝑇 𝑂𝐺
Substitute 𝑥 50 = 24 30
Simplify 𝑥 50 = 4 5
Solve x(5) = 50(4)  5x = divide by x= 40

6. Example Find the value of x. D A x cm 3 cm 16 cm G 4 cm C 2 cm 8 cm
B E

7. Exit Ticket Find the value of x. D A 10 cm 4 cm 12.5 cm G x cm C
B E

8. Questions?

9. Worksheet