Final answer:
Triangle AABD is congruent to triangle ACBD.
Step-by-step explanation:
Triangle AABD is congruent to triangle ACBD.
Since triangle ABC is an isosceles triangle with a right angle at B, the base angles A and C are congruent. Therefore, angle ABD is congruent to angle CBD. Since BD is parallel to AC, angle BDA is a right angle.
By the Angle-Angle Similarity Postulate, triangles AABD and ACBD are congruent.