Answer:
Given: 
ΔABC is an isosceles triangle
AD is an angle bisector of ∠A
Statement | Proof
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ΔABC is an isosceles triangle Given; Definition of an 
 isosceles triangle.
AD bisects ∠ABC Definition of a angle bisector.
AD ≅ AD Reflexive Property
AD bisects BC Definition of a line segment bisector
BD ≅ CD " "
∠BDA ≅ ∠ADC Triangle Bisector Theorem
What has been proven so far:
AD ≅ AD ; ∠BDA ≅ ∠CDA ; BD ≅ CD
Based on this information, 
ΔABD ≅ ΔACD Side-Angle-Side Theorem
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