Please help with geometry proofs Given: ∆ABC is an isosceles triangle where AB = BC

Prove: m∠BAC = m∠BCA

Statement Reason
1. Let ∆ABC be an isosceles
triangle where AB = BC. given
2. Create point D on side so
that bisects ∠ABC as shown.

constructing an angle bisector
3. m∠ABD = m∠CBD
4. BD = BD Reflexive Property of Equality
5. ∆ABD ≅ ∆CBD SAS
6. m∠BAC = m∠BCA Corresponding angles of congruent triangles have equal measures.

What is the reason for statement 3 in this proof?

A.
definition of angle bisector

B.
Alternate Interior Angles Theorem

C.
Corresponding Angles Theorem

D.
Corresponding angles of congruent triangles are congruent.