10/25/2015
Splash Screen
Over Lesson 4–3
Write a congruence
statement for the
triangles.
A. ΔLMN  ΔRTS
B. ΔLMN  ΔSTR
C. ΔLMN  ΔRST
D. ΔLMN  ΔTRS
5-Minute Check 1
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10/25/2015
Over Lesson 4–3
Given that ΔABC  ΔDEF, which of the following
statements is true?
A. A  E
B. C  D
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C. AB  DE
D. BC  FD
5-Minute Check 6
Over Lesson 4–3
• Side-Side-Side (SSS) Triangle
Congruence
• Flow Proofs
• Side-Angle-Side (SAS) Triangle
Congruence
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Concept 1
• Flow
Proof – A
method or
tool
(flowchart)
used to
prove
geometric
statements
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Which information
___ ___ is missing from the flowproof?
Given: AC  AB
D is the midpoint of BC.
Prove: ΔADC  ΔADB
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A. AC  AC
B. AB  AB
C. AD  AD
D. CB  BC
Example 1 CYP
Use SSS to Prove Triangles Congruent
Write a flow proof.
___ ___ ___
___
Given:
QU  AD, QD  AU
Prove:
ΔQUD  ΔADU
Example 1
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Concept 2
Use SAS to Prove Triangles are
Congruent
ENTOMOLOGY The wings of one type of moth form
two triangles. Write a two-column proof to prove
that ΔFEG  ΔHIG if EI  FH, and G is the midpoint
of both EI and FH.
Example 3
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Use SAS to Prove Triangles are
Congruent
Given: EI  FH; G is the midpoint of
both EI and FH.
Prove: ΔFEG  ΔHIG
Example 3
The two-column proof is shown to prove that
ΔABG  ΔCGB if ABG  CGB and AB  CG.
Choose the best reason to fill in the blank.
Proof:
Statements
1.
Reasons
1. Given
2.
2. ? Property
3. ΔABG ΔCGB
A. Reflexive
3. SSS
B. Symmetric
C. Transitive
D. Substitution
Example 3
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Use SAS or SSS in Proofs
Write a flow proof.
Prove: Q  S
Example 4
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