## Elementary Geometry for College Students (6th Edition)

Using method ASA with 2 congruent pairs of angles and a congruent pair of included side, it is proved that $\triangle ABC\cong\triangle DBC$.
Since $\angle 1$ and $\angle 2$ are both right angles, it is deduced that $\angle 1\cong\angle 2$. It is also mentioned that - $\overline{AB}\cong\overline{BD}$ - $\angle A\cong\angle D$ We now have 2 angles and the included side of $\triangle ABC$ are congruent with 2 angles and the included side of $\triangle DBC$. Therefore, according to method ASA, $\triangle ABC\cong\triangle DBC$.