1. 2. Definition of congruent segments AB = CD 2.
Use the Segment Addition Postulate
Proof:
Statements Reasons 1.
1. Given
AB  CD
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2. Definition of congruent segments
AB = CD 2.
3. Reflexive Property of Equality
BC = BC 3.
4. Segment Addition Postulate
AB + BC = AC 4.
Example 1

2. 5. Substitution Property of Equality 5. CD + BC = AC
Use the Segment Addition Postulate
Proof:
Statements Reasons
5. Substitution Property of Equality
5. CD + BC = AC
6. Segment Addition Postulate
CD + BC = BD 6.
7. Transitive Property of Equality
AC = BD 7.
8. Definition of congruent segments 8.
AC  BD
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Example 1