Given: δabc is an isosceles triangle where ab = bc.
prove: m∠bac = m∠bca

proof:
statement reason
1. let δabc be an isosceles triangle where ab = bc. given
2. create point d on so that bisects ∠abc as shown. constructing an angle bisector
3. m∠abd = m∠dbc definition of angle bisector
4. bd = bd
5. δabd ≅ δcbd sas
6. m∠bac = m∠bca corresponding angles of congruent triangles are equal.

what is the reason for statement 4 in this proof?
a.
transitive property of equality
b.
definition of midpoint
c.
definition of parallel lines
d.
reflexive property of equality