## Geometry: Common Core (15th Edition)

$m \angle A = m \angle D$
We are given that $\triangle ABC$ ∼ $\triangle DBF$. In similar triangles, corresponding angles are congruent, and corresponding sides are proportional. Let us list the congruent angles in the two triangles: $\angle A ≅ \angle D$ $\angle B ≅ \angle B$ $\angle C ≅ \angle F$ Therefore, $m \angle A = m \angle D$.