Question 56
Let $ABCD$ be a trapezium with bases $\overline{AB}$ and $\overline{CD}$, such that $ABC$ is an acute-angled triangle. Let $O$ be the centre of the circle circumscribed to the triangle $ABC$, and let $E$ be the intersection of lines $OB$ and $CD$. If $\angle DBC = \angle CEB + 10^\circ$, find the measure of the angle between the diagonals of $ABCD$.