Warm Up

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Warm Up
Lesson Presentation
Lesson Quiz
Holt McDougal Geometry
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• Warm Up
• 1. Name the angle formed by AB and AC.
• 2. Name the three sides of ?ABC.
• 3. ?QRS ? ?LMN. Name all pairs of congruent
  corresponding parts.

Possible answer ?A
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Objectives
Apply SSS and SAS to construct triangles and
solve problems. Prove triangles congruent by
using SSS and SAS.
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Vocabulary
triangle rigidity included angle
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In order to prove polygons are congruent, you
must show that corresponding sides are congruent.
Triangle rigidity gives a short cut to show
triangles are congruent.
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For example, you only need to know that two
triangles have three pairs of congruent
corresponding sides. This can be expressed as the
following postulate.
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Example 1 Using SSS to Prove Triangle Congruence
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Is ?ABC ? ?DBC? Explain.
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Check It Out! Example 1
Is ?ABC ? ?CDA? Explain.
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It can also be shown that only two pairs of
congruent corresponding sides are needed to prove
the congruence of two triangles if the included
angles are also congruent.
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COPY THIS SLIDE
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Example 2 Engineering Application
Is ?XYZ ? ?VWZ? Explain.
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Check It Out! Example 2
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Is ?ABC ? ?DBC? Explain
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Examples
Which postulate, if any, can be used to prove the
triangles congruent?
3.
2.
none
SSS
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Classwork/Homework

• 4.5 SSS, SAS, ASA, AAS W/S