1. Agenda Investigation 8-3 Proving Triangles are Similar Class Work
Homework

2. Warm Up 1 State if the following figures are similar
2 The two triangles are similar. Solve for x.

3. Homework Check
3. 3b 4. 4/3 5. b/4 6. b/a 7. 3/a 8. 4a 9. 7/ /7 11. (b+4)/ / : : :3

4. Homework Check contd 1.JHY 2. R 3. JXY 4. HY 5. JT 6. HY
9. yes, KLMJ~PQNO; 3/ yes; ABCD~FGHE;4/5
11. No; corr angles are not congruent
12. yes; ABC~FED; 7/5
13. x=4, y= x=20, y=17.5, z=7.5
15. x=16, y=4.5, z= x=6, y=8, z=10

5. Investigation: Triangles with Two Pairs of Congruent Angles
With a partner, complete the Investigation Worksheet.
Answer both questions

6. 8-3 Proving Triangles are Similar
3 ways to prove Triangles are Similar:
AA ~
If two angles of one triangle are congruent to two angles of another triangle, then the triangles are similar
Similarity Statement:

7. 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:

8. 3. SSS ~
If all 3 corresponding sides of two triangles are proportional, then the triangles are similar Similarity Statement:

9. Indirect Measurement using similar triangles often uses one of these two facts:
Light reflects off a mirror at the same angles at which it hits the mirror.
Similar By:

10. 2. Similar Triangles are formed by figures and their shadows Similar By:

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

19. Class Work
8-3 Practice in Book
Problems 1-9

20. Homework
Complete the worksheet