Download 7.3 Proving Triangles Similar

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7.3 Proving Triangles Similar
Related Topic
• Remember we had to prove triangles
congruent? Proving triangles similar is similar
to proving triangles congruent but different
• The theorems to prove triangles similar are
different
Postulate 7.1 Angle-Angle similarity
(AA~) Postulate
• If two angles of one triangle are congruent to
two angles of another triangle, then the
triangles are similar
P
T
R
S
L
TRS ~ PLM
M
Theorem 7.1 Side-Angle-Side Similarity
(SAS~) Theorem
• If an angle of one triangle is congruent to an
angle of a second triangle, and the sides
including the two angles are proportional,
then the triangles are similar
• Examples:
Notice the difference
Theorem 7.2 Side-Side-Side (SSS~)
Theorem
• If the corresponding sides of two triangles are
proportional, then the triangles are similar
• Examples:
Are the triangles similar? Why? Write
the similar statement
W
V
S
45
45
R
B
Are the triangles similar? Why?
Write the similar statement
P
X
8
6
Q
R
4
Z
Y
3
If the triangles are similar, find DE
A
12
10
B
24
D
C
16
18
E
Vocabulary
• Indirect measurement – You use similar
triangles and measurements to find distances
that are difficult to measure directly
Example of indirect measurement
Homework/Classwork
• Pgs 385-387 #1,2, 4-20, 24-27, 32