1. Warm up…
checkpoint quiz page 429 #’s 1 – 10

2. 8.3 Proving Triangles Similar

3. SWBAT… To use AA, SAS, and SSS similarity statements
To apply AA, SAS and SSS similarity statements.

4. Investigation: triangles w/ 2 pairs of congruent angles
Use page 432 and complete the investigation in the blue box.
We’ll have a class discussion in 4 minutes.

5. Angle – Angle Similarity (AA~) Postulate
If two angles of one triangle are congruent to two angles of another triangle, then the triangles are similar. A B C R S T
If angles A and R are congruent and angles B and S are congruent (mark them), Then triangle ABC ~ triangle RST

6. Example 1
MX is perpendicular to AB. Explain why the triangles are similar. Write a similarity statement. M K B A X

7. Side Side Side Similarity
THEOREM: if the corresponding sides of two triangles are proportional, then the triangles are similar. A B C R S T

8. Example 2
If AB = 18, BC = 12, AC = 21, RS = 6, ST = 4, RT = 7 are the triangles similar? A B C R S T

9. Side – Angle – Side (SAS ~)
If the measures of two sides are proportional to the measures of two corresponding sides of another triangle and the included angles are congruent, then the triangles are similar. A B C R S T

10. Example 3 A B C R S T 6 12 4 8
Are the two triangles similar?

11. Example 4 In the figure AB || DC,
Determine which triangles are similar. C B E D A

12. Example 5
Given UT || RS, find SQ and QU. U R
2x + 10 10 4
X + 3 S T

13. Example 6
If you wanted to measure the height of the Sears tower in Chicago, you could measure a 12-foot light pole and measure its shadow. If the length of the shadow was 2 feet and the shadow of the Sears Tower was 242 feet, what is the height of the Sears Tower?

14. Class work… Page 435 – 436 #’s 1 – 19, 23, 45 – 48
We do have a short quiz Monday on what we’ve covered in Ch. 8
Chapter 8 test is Friday of next week.