1. Secondary Math 2 8.3/8.4 – Similarity
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8.3/8.4 – Similarity

2. Warm - UP List the 4 ways to prove triangles congruent
Are the triangles below congruent? If so, how do you know?
If they are congruent, write a congruence statement.

3. Turn in 8.1 Questions 8.2 – Triangle Congruence

5. What you will learn
I will be able to determine if two shapes are similar. I will be able to determine the scale factor between to similar shapes.

6. Similarity
Same Shape DIFFERENT SIZE (dilated)
Proportions

7. Triangle Similarity Shortcuts - PPP
3 pairs of proportional sides E F D 4
9.6
10.4 A B C 5 12 13

8. Triangle Similarity Shortcuts - PAP
2 pairs of proportional sides and congruent angles between them G H I 5 7
70 L J K
7.5
10.5
70

9. Triangle Similarity Shortcuts - AA
2 pairs of congruent angles Q P R
70
50 M N O
70
50
Why does AA work?

10. Practice! Are they similar?

11. Scale Factor

12. Calculating Scale Factor (smaller to bigger)
Find two corresponding sides, and write the ratio of the two sides.

13. More Scale Factor (smaller to bigger)
14.

14. Solve for x.
1. 2.
3. 4.

15. Solving Similar Polygon Problems
Proportional Statements:
5 4 = = E F D 4
9.6
10.4 A B C 5 12 13

16. More Proportions practice!
17.
22.