Lesson 7-3 Proving Triangles Similar (page 134)

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Lesson 7-3 Proving Triangles Similar (page 134)

• I can use and apply AA, SAS, SSS similarity
  statements

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3 Methods to Determine if Triangles are
Similar 1. Angle-Angle (AA) Similarity
Postulate 2. Side-Side-Side (SSS) Similarity
Theorem 3. Side-Angle-Side (SAS) Similarity
Theorem
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Angle-Angle (AA) Similarity Thm
AA Similarity Postulate
If two angles of one triangle are congruent to
two angles of another triangle, then the
triangles are similar.
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Do Now
Using (AA) Similarity Theorem
Explain why the triangles are similar and write a
similarity statement.
?R ? ?V Given (measures are equal) ?RSW ?
?VSB Vertical ?s ?RSW ?VSB AA Postulate
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Side-Angle-Side (SAS) Similarity Thm
SAS Similarity 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.
?ABC ? ?EBD Vertical angles AB 12
2 EB 18 3 CB 16
2 DB 24 3
Proportional
?ABC ?EBD by SAS
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Side-Side-Side (SSS) Similarity Theorem
SSS Similarity Theorem
If the corresponding sides of two triangles are
proportional, then the triangles are .
Are all sides proportional?
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Indirect measurement is

• When you can use similar triangles and
  measurements to find distances that are difficult
  to measure directly.

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Indirect Measurement using Similarity
Explain why the triangles are , then find the
distance represented by x.
AA Postulate 220 yards
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Triangle Congruence vs. Similarity

• How are the triangle similarity postulate and
  theorems alike and how are they different from
  triangle congruence postulates?

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Activities

• Example 2
• Quick check 2 and 3 in partners
• Prepare a written explanation of how you would
  measure indirectly the height of the classroom.
• Worksheet activity