Han wrote a proof that triangle BCD is congruent to triangle

Last updated: 7/8/2022

Han wrote a proof that triangle BCD is congruent to triangle DAB. Han's proof is incomplete. How can Han fix his proof? Line AB is parallel to line DC and cut by transversal DB. So angles CDB and ABD are alternate interior angles and must be congruent. Side DB is congruent to side BD because they're the same segment. Angle A is congruent to angle because they're both right angles. By the Angle-Side-Angle Triangle Congruence Theorem, triangle BCD is congruent to triangle DAB.