Agenda1. Investigation

2. 8-3 Proving Triangles are Similar

3. Class Work

4. Homework

Warm Up1 State if the following figures are similar

2 The two triangles are similar. Solve for x.

Homework Check3. 3b 4. 4/3 5. b/4 6. b/a 7. 3/a 8. 4a

9. 7/4 10. 3/7 11. (b+4)/4 12. 4 13. 5/3

14. 4 15. 6.875 16. 7.2 17. 7.2 18. 7.5

19. 14 20. 7 26. 13:6 27. 5:4 28. 4:3

Homework Check contd

1.JHY 2. R 3. JXY 4. HY 5. JT 6. HY

9. yes, KLMJ~PQNO; 3/5 10. yes; ABCD~FGHE;4/5

11. No; corr angles are not congruent

12. yes; ABC~FED; 7/5

13. x=4, y=3 14. x=20, y=17.5, z=7.5

15. x=16, y=4.5, z=7.5 16. x=6, y=8, z=10

Investigation: Triangles with Two Pairs of Congruent AnglesWith a partner, complete the Investigation

Worksheet.

Answer both questions

8-3 Proving Triangles are Similar

3 ways to prove Triangles are Similar:

1. AA ~If two angles of one triangle are congruent to two angles of

another triangle, then the triangles are similar

Similarity Statement:

2. SAS ~

If 2 sides of a triangle are proportional to two sides of another triangle AND the included (in between) angles are congruent, then the triangles are similar.

Similarity Statement:

3. SSS ~

If all 3 corresponding sides of two triangles are proportional, then the triangles are similar

Similarity Statement:

Indirect Measurement using similar triangles often uses one of these two facts:

1. Light reflects off a mirror at the same angles at which it hits the mirror.

Similar By:

2. Similar Triangles are formed by figures and their shadows

Similar By:

Examples:

For each of the following, explain why the triangles are similar and write a similarity statement

Class Work8-3 Practice in Book

Problems 1-9

Homework Complete the worksheet