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Applied Geometry
Lesson: 9 – 3
Similar Triangles
Objective:
Learn to use AA, SSS, and SAS similarity tests for triangles.
Review
Congruent Triangles

Triangles whose sides and angles are
congruent.
Tests for congruence
SSS
 SAS
 ASA
 AAS

New – Tests for similarity
AA Similarity
If two angles of one triangle are
congruent to two corresponding angles
of another triangle, then the triangles
are similar.
SSS similarity
If the measures of the sides of a triangle
are proportional to the measures of the
corresponding sides of another triangle,
then the triangles are similar.
SAS Similarity
If the measures of two sides of a triangle are
proportional to the measures of two
corresponding sides of another triangle and
their included angles are congruent, then the
triangles are similar.
Determine whether the triangles are
similar. If so, tell which similarity test
is used and complete the statement.
6 10 14


9 15 21
JMP SSS similarity
Determine whether the triangles are
similar. If so, tell which similarity test
is used and complete the statement.
Not similar since SSS, SAS, or AA similarity
tests prove true.
Determine whether the triangles are
similar. If so, tell which similarity test
is used and complete the statement.
Not similar since sides are not proportional.
Find the value of x.
x 9

5 3
3x  45
x  15
Find the values of x & y
12 5

x 15
180  5x
36  x
13 5

y 15
195  5 y
39  y
shadow 0.4 2 shadow

object 1.5 x object
0.4x  3
x  7.5
Flag pole is 7.5 meters tall.
Homework
Pg. 365 1 – 5 all, 6 – 22 E