1. 7.3 Similar Triangles

2. Objectives/Assignment
Identify similar triangles.
Use similar triangles to solve problems

3. Identifying Similar Triangles
In this lesson, you will continue the study of similar polygons by looking at the properties of similar triangles.

4. Ex. 1: Writing Proportionality Statements
Given, ∆BTW ~ ∆ETC.
Write the statement of proportionality.
Find m  TEC.
Find ET
Find BE.
34°
79°

5. Ex. 1: Writing Proportionality Statements
In the diagram, ∆BTW ~ ∆ETC.
Write the statement of proportionality.
34° ET TC CE = = BT TW WB
79°

6. Ex. 1: Writing Proportionality Statements
In the diagram, ∆BTW ~ ∆ETC.
Find m  TEC.
B  TEC, SO
m  TEC = 79°
34°
79°

7. Ex. 1: Writing Proportionality Statements
In the diagram, ∆BTW ~ ∆ETC.
Find ET and BE.
34° CE ET
Write proportion. = WB BT 3 ET
Substitute values. = 12 20
3(20) ET
Multiply each side by 20. =
79° 12 5 = ET
Simplify.
Because BE = BT – ET, BE = 20 – 5 = 15. So, ET is 5 units and BE is 15 units.

8. Angle-Angle Similarity Postulate

9. Notes
Solution:

10. Notes

11. Notes

12. Take Notes:
Solution:
12x = 60
x = 5
12y = 40
y = 3.3

13. Take Notes:
Solution:
6x = 30
x = 5
3y + 15 = 24
y = 3

14. Take Notes:
Solution:
15x = 240
x = 16
39y = 780
y = 20

15. Proofs:

16. Proofs:

17. Practice:
Solution:
9x = 72
x = 8

18. Practice:
Solution:
16x = 36 * 20
16x = 720
x = 45

19. Practice:
Solution:
32x = 800
x = 25

20. Practice:
Solution:
12x = 48
x = 4

21. Practice:
Solution:
5x - 5 = 30
5 x = 35
x = 7

22. Practice:
Solution:
8x - 16 = 40
8 x = 56
x = 7

23. Practice:
Solution:
16x - 8 = 56
16 x = 64
x = 4

24. Practice:
Solution:
4x - 8 = 12
4 x = 20
x = 5