∵AB∥CD∴∠ABC=∠DCB(两直线平行，内错角相等）∵,∠ABE=∠DCF∴∠ABC-∠ABE=∠DCB-∠DCF即∠EBC=∠FCB∴BE∥CF(内错角相等，两直线平行）
∵AB〃CD∴∠ABC=∠BCD∵∠ABE=∠DCF∴∠ABC-∠ABE=∠DCB-∠DCF即∠EBC=∠FDB∴BE〃CD
