2. Consider the quadrilateral $A B C D$ where $m(\varangle A B C)=90^{\circ},[A C] \equiv[A D]$ and $m(\Varangle B A C) \equiv m(\Varangle C A D)=20^{\circ}$. Consider the point $E \in(A C)$ such that $D E \perp A C$. Determine the measure of the angle $\Varangle E B C$.
2. We have $\triangle A B C \equiv \triangle A E D$ (I.U.), from which $[A B] \equiv[A E] ; \quad 3 p$

Triangle $A B E$ is isosceles and $m(\angle A B E)=80^{\circ}$; 3p

We obtain $m(\angle E B C)=10^{\circ}$

$1 p$