Question 108
Let $ABC$ be a triangle of which $O$ is the center of the circumscribed circle. We note $\ell$ a straight line perpendicular to the line $(AO)$. The right $(\ell)$ intersects the sides $(AB)$ and $(AC)$ in the points $D$ and $E$. Show that points $B$, $C$, $E$ and $D$ are cocyclic.