证明:∵$AB + BD = DC,$$BD = DE,$
$DC = DE + CE,$∴$AB = CE$
∵$AD$是边$BC$上的高,∴$AD\perp BC$
∴$∠ADB = ∠ADE = 90°$
$ $在$\triangle ADB$和$\triangle ADE$中
$\begin {cases}BD = ED\\∠ADB = ∠ADE\\AD = AD\end {cases}$
∴$\triangle ADB≌\triangle ADE(S AS)$
∴$AB = AE,$即$AE = CE$
∴点$E$在线段$AC$的垂直平分线上