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9.1 Practice with Examples

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Apr 22, 2010 ... 160. Geometry. Practice Workbook with Examples ... drawn to the hypotenuse of a right triangle and use a geometric mean to solve problems.
MCRBG-0901-PE.qxd

3-16-2001

3:03 PM

Page 160

LESSON

9.1

NAME _________________________________________________________ DATE ____________

Practice with Examples For use with pages 527–534

GOAL

Solve problems involving similar right triangles formed by the altitude drawn to the hypotenuse of a right triangle and use a geometric mean to solve problems Theorem 9.1 If the altitude is drawn to the hypotenuse of a right triangle, then the two triangles formed are similar to the original triangle and to each other. Theorem 9.2 In a right triangle, the altitude from the right angle to the hypotenuse divides the hypotenuse into two segments. The length of the altitude is the geometric mean of the lengths of the two segments. Theorem 9.3 In a right triangle, the altitude from the right angle to the hypotenuse divides the hypotenuse into two segments. The length of each leg of the right triangle is a geometric mean of the lengths of the hypotenuse and the segment of the hypotenuse that is adjacent to the leg.

EXAMPLE 1

Finding the Height of a Triangle Consider the right triangle shown.

B

a. Identify the similar triangles.

D

11.6

b. Find the height h of ABC.

6 h

SOLUTION a. ABC~CBD~ACD

A

C

10

Sketch the three similar right triangles so that the corresponding angles and sides have the same orientation. B

C

B

C

D A

D A

C

b. Use the fact that ABC~CBD to write a proportion.

Chapter 9

CD CB  AC AB h 6  10 11.6 11.6h  610 h  5.2

160

Geometry Practice Workbook with Examples

Corresponding side lengths are in proportion. Substitute. Cross product property Solve for h.

Copyright © McDougal Littell Inc. All rights reserved.

MCRBG-0901-PE.qxd

3-16-2001

3:03 PM

LESSON

9.1

CONTINUED

Page 161

NAME _________________________________________________________ DATE ____________

Practice with Examples For use with pages 527–534

Exercises for Example 1 Find the height, h, of the given right triangle. 1.

Y

2. 2

X

5

3.

E

N

2

4.4 6.7

h

P

3

D

h W

G 2

F

h M

Z

4

5.9

7.8 Q

EXAMPLE 2

Using a Geometric Mean Find the value of each variable. a.

b. x

1 3 y

10

4

SOLUTION a. Apply Theorem 9.3.

10  4 x  x 4 x2  56

Copyright © McDougal Littell Inc. All rights reserved.

3 y  y 1 y2  3 y  3

Chapter 9

x  56  4  14  214

b. Apply Theorem 9.2.

Geometry Practice Workbook with Examples

161

MCRBG-0901-PE.qxd

3-16-2001

LESSON

9.1

CONTINUED

3:03 PM

Page 162

NAME _________________________________________________________ DATE ____________

Practice with Examples For use with pages 527–534

Exercises for Example 2 Find the value of each variable to the nearest tenth. 4. 6 h 7

5.

1 11 x

6.

10 13

Chapter 9

y

162

Geometry Practice Workbook with Examples

Copyright © McDougal Littell Inc. All rights reserved.