證明：在$\triangle AOB$與$\triangle COD$中，
$\begin{cases}\angle A = \angle C \\OA = OC \\\angle AOB = \angle COD\end{cases}$
$\therefore \triangle AOB\cong\triangle COD(ASA)，$
$\therefore OB = OD，$
$\therefore$點(diǎn)$O$在線段$BD$的垂直平分線上.
$\because BE = DE，$
$\therefore$點(diǎn)$E$在線段$BD$的垂直平分線上，
$\therefore OE$垂直平分$BD.$
