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HG6­5.notebook
March 02, 2012
Chapter 6.5 - Prove Triangle Similarity using SSS and SAS
Are all equilateral triangles similar?
Side­Side­Side Similarity Theorem (SSS)
If the corresponding side lengths of two triangles are proportional,
then the triangles are similar.
Ex. 1: Is DEF or GHJ similar to ABC?
B
12
8
16
C
10
9
6
E
A
H
F
12
D
J
8
16
G
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HG6­5.notebook
March 02, 2012
Ex. 2:
Find x so that ABC ~ DEF
E
B
18
x ­ 1
4
A
8
C
D
3(x + 1)
F
7 = x
Side­Angle­Side Similarity Theorem (SAS)
If an angle of one triangle is congruent to the angle of another
triangle and the lengths of the sides including the angles are
proportional, then the triangles are similar.
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HG6­5.notebook
March 02, 2012
Similarity Postulates and Theorems
AA
SSS
A
C
A
F
D
≅
C
D
E
B
F
C
A
BC
AC
AB
= =
DF
EF
DE
≅
A D
B
E
B
E
B
SAS
B
F
D
≅
E
BC
AB
=
EF
DE
E
Ex. 3: Which postulate or theorem would make these triangles similar?
Write the similarity statement.
E
A
15
18
C
9
B
30
D
3
HG6­5.notebook
March 02, 2012
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