1. Chapter 8 Lesson 3 Objective: Objective: To apply AA, SAS, and SSS similarity.

2. Name the postulate or theorem you can use to prove the triangles congruent. 1. 2. 3. SSS SAS ASA

3. Name the SIMILARITY postulate or theorem you can use to prove the triangles congruent. 1. 2. 3. AA~ SAS~ SSS~

4. Example 1: Finding Lengths in Similar Triangles Explain why the triangles are similar. Write a similarity statement. Then find DE. Explain why the triangles are similar. Write a similarity statement. Then find DE. Because vertical angles are congruent. ΔABC ~ ΔEBD by the SAS~ Theorem.

5. Example 2: Finding Lengths in Similar Triangles Find the value of x in the figure. Find the value of x in the figure.

6. Indirect Measurement is when you use similar triangles and measurements to find distances that are difficult to measure directly.

7. Example 3: Indirect Measurement Geology Ramon places a mirror on the ground 40.5 ft from the base of a geyser. He walks backwards until he can see the top of the geyser in the middle of the mirror. At that point, Ramon's eyes are 6 ft above the ground and he is 7 ft from the image in the mirror. Use similar triangles to find the height of the geyser. ∆HTV ~ ∆JSV The geyser is about 35 ft. high.

8. Example 4: Indirect Measurement In sunlight, a cactus casts a 9-ft shadow. At the same time a person 6 ft tall casts a 4-ft shadow. Use similar triangles to find the height of the cactus. X 9 6 4

9. Assignment Page 435 #10-21, 23, 28-39