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DO NOW- Complete #1-5 on the
proofs worksheet that you picked
up from the back of the classroom.
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Use the reasons below to complete
the proofs for 4&5
Number 4
Number 5
 Definition of Midpoint
 Segment Addition
 Given
 Transitive Property
 Given
 Subtraction
 Substitution
 Given
 Definition of Congruence
 Definition of Congruence
 Definition of Congruence
 Segment Addition
 Substitution
 Definition of Congruence
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Given AB = BC
Prove AC=2BC
Statements
Reasons
1) AB=BC
2)
3) BC+BC=AC
4)
5) AC=2BC
1)
2) Segment Addition
3)
4) Simplify
5)
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Given AB = BC
Prove AC=2BC
Statements
Reasons
1) AB=BC
2) AB+BC=AC
3) BC+BC=AC
4) 2BC=AC
5) AC=2BC
1)Given
2) Segment Addition
3) Substitution BC for AB
4) Simplify
5) Reflexive Property
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Try on your own:
Given JK = KL
Prove JL=2JK
J
K
L
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2.8 Proving Angle Relationships
Example:
USING
THE ANGLE ADDITION
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POSTULATE PRACTICE
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Given: Angle ABC is a right Angle
Prove: Angle ABD and Angle DBC are complementary
Given:
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Angles 1 and 2 form a linear pair.
M<1 + M<3 = 180
Prove Ð2 @ Ð3
Statements
Reasons
1) Angles 1 & 2 are a LP
1)
2)
2) Given
3)
3) The supplement theorem
4) Angles 1 and 3
are supplementary
4)
5)
5) congruent supplements thm
Given:
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Angles 1 and 2 form a linear pair.
M<1 + M<3 = 180
Prove Ð2 @ Ð3
Statements
1) Angles 1 and 2 are a LP
2) M<1 + M<3 = 180
3) Angles 1 and 2 are
supplementary
4) Angles 1 and 3
are supplementary
5) 2 and 3 are congruent
Reasons
1) Given
2) Given
3) Supplement Thm
4) Def of
supplementary angles
5) congruent supplements thm
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You try: