9. Given a rectangle $A B C D$, let $E$ be the point on the diagonal $B D$ such that the line $A E$ is perpendicular to $B D$. Knowing that the angle $\widehat{B A C}$ is $28^{\circ}$, what will be the measure of the angle $\widehat{D A E}$?
(A) $24^{\circ}$
(B) $36^{\circ}$
(C) $32^{\circ}$
(D) $28^{\circ}$
(E) $30^{\circ}$
(9) The correct answer is $(D)$.

The angle $\widehat{A C B}$ is complementary to $\widehat{B A C}$ (indeed, the triangle $A B C$ is right-angled at $B$). Since the angle $\widehat{A D E}$ is congruent to $\widehat{A C B}$ and is complementary to $\widehat{D A E}$ (since the triangle $A E D$ is right-angled at $E$), it follows that the angle $\widehat{D A E}$ is congruent to $\widehat{B A C}$ and also measures $28^{\circ}$. Question proposed by Carlo Cassola.