1. Similar Right Triangles
Chapter 8 Right Triangles and Trigonometry
Chapter 8 Test on Thursday 2/11
Similar Right Triangles
Section 8.1

2. Find the geometric mean between two numbers.
Solve problems involving relationships between part of a right triangle and the altitude to its hypotenuse.
geometric mean
Standard 4.0 Students prove basic theorems involving congruence and similarity. (Key)
Lesson 1 MI/Vocab

3. Geometric Mean If x is the Geometric Mean of a and b, then:
Find the Geometric Mean of 5 and 20.

4. B. Find the geometric mean between 25 and 7.
Definition of geometric mean
Cross products
Take the positive square root of each side.
Simplify.
Use a calculator.
Answer: The geometric mean is about 13.2.
Lesson 1 Ex1

5. A. 3.9 B. 6 C. 7.5 D. 4.5 A. Find the geometric mean of 3 and 12. A B
Lesson 1 CYP1

6. A C D
Theorem 8 – 1: If the altitude is drawn from the vertex of the right angle of a right triangle to its hypotenuse, then the two triangles formed are similar to the given triangle and to each other. C B C D A D B

7. CBD ~ ABC
ACD ~ ABC
CBD ~ ACD

8. 2. Sketch two-”mini-me’s” of the original.
Special Update!!!!!! Unpacking the triangles (without having the think too hard.) C A B
2. Sketch two-”mini-me’s” of the original.
1. Sketch the large triangle first, copying the vertices.

9. Point D will go on top of the min-me’s A B D
Special Update!!!!!! Unpacking the triangles (without having the think too hard.) C
Point D will go on top of the min-me’s A B D
2. Sketch two-”mini-me’s” of the original. D

10. Special Update!!!!!! Unpacking the triangles (without having the think too hard.)B D C A
Now study the pattern! D C B

11. K J M L K J L K M

12. S Q R T S Q T S R

13. In a right triangle, the altitude from the right angle to the hypotenuse divides the hypotenuse into two segments.

14. Theorem 8.2
The length of the altitude is the geometric mean of the lengths of the two segments.

15. Altitude and Segments of the Hypotenuse
In ABC, BD = 6 and AD = 27. Find CD. Δ 6 27 x
Answer: CD is about 12.7
Lesson 1 Ex2

16. Find EG. Round your answer to the nearest tenth.
B. 36
C. 4.7
D. 8.5 A B C D
Lesson 1 CYP2

17. Theorem 8.3
The length of each leg of the right triangle is the geometric mean of the lengths of the hypotenuse and the segment of the hypotenuse that is adjacent to the leg.

18. = 20 Hypotenuse and Segment of Hypotenuse Find c and d in ΔJKL.
Lesson 1 Ex4

19. = 20 25 = 11.2 Hypotenuse and Segment of Hypotenuse
Find c and d in ΔJKL.
= 20
= 11.2 25
Lesson 1 Ex4

20. A. Find e to the nearest tenth.
B. 24
C. 17.9
D. 11.3 A B C D
Lesson 1 CYP4

22. Homework
Chapter 8-1
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