Final answer:
To prove ADB = CDB, we can use the Alternate Interior Angles Theorem. By substituting DAB for DCB, we can conclude that ADB = CDB using the Transitive Property of Equality.
Step-by-step explanation:
To prove: ADB = CDB
Given: BD is parallel to AC and DAB = DCB
Since BD is parallel to AC, we have ADB = DCB by the Alternate Interior Angles Theorem.
Also, since DAB = DCB, we can substitute DCB as DAB in the equation ADB = DCB, giving us ADB = DAB.
Therefore, ADB = CDB by the Transitive Property of Equality.