7.4 similarity in right triangles - poudre school...
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7.4 Similarity in Right Triangles
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February 18, 2010
Feb 117:46 AM
7.4 Similarity in Right Triangles
Objective: To find and use relationships in similar right triangles.
7.4 Similarity in Right Triangles
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Warmup
A B
C
D
Name the three right triangles in the figure below.
7.4 Similarity in Right Triangles
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A B
C
D
A D
C
D
B
C A
BC
Similarity in Right Triangles
7.4 Similarity in Right Triangles
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DA
C
C D
B
C A
B A B
C
c
a
rs
h
D
b
Appropriately label each side of the three similar triangles. Then give the similarity statement.
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a
rs
hb
s
hbr
h
aa c
b
Write the proportionality statements for each set of similar triangles.
Short leg & Hypotenuse Long leg & Hypotenuse Long leg & Short leg
Large to Medium
Large to Small
Medium to Small
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Example #1
Step 1: Separate each triangle and orient correctly.
Step 2: Set up the proportionality statement.
Step 3: Solve the proportion.
y
5
4
yx
x4 + 5
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Example #2
Step 1: Separate each triangle and orient correctly.
Step 2: Set up the proportionality statement.
Step 3: Solve the proportion.
x16
yx4
y 12
7.4 Similarity in Right Triangles
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New Vocabulary: Geometric Mean
The geometric mean of a and b is the positive number x such that . ax b
x=
Find the geometric mean of:
3 and 18:
4 and 9:
5 and 9:
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Physical Representation of Geometric Mean
93
h
9
h3
h
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Geometric Mean (continued)
106
b
6
b
16
b
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52
a
a 10 a5
Geometric Mean (continued)
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Example #3
A service station will be built on the highway, and a road will connect it with Cray. How far from Blare should the service station be located so that the proposed road will be perpendicular to the highway?
a.
How long will the new road be?b.
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We done.(except . . .)
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Homework
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