四边形ABCD是平行四边形,∠D=∠B,∴∠B=∠ACE.在△ACD和△ACF中,∠CAF=∠CAD,∠D=∠ACE.∴△ACD∽△ACF.∴AF/AC=AC/AD,AF=AC²/AD=36/9=4.在△AEC和△BEC中,∠E=∠E,∠B=∠ACE.∴△AEC∽△BEC.∴BE/EC=BC/AC,BE=...