①∵Rt△ABE≌Rt△ADF{斜边及一直角边对应相等},∴BE=DF.
②∵AO、EF互为中垂线{已知AE=AF,∠FAO=90º-∠DAF=90º-∠BAE=∠EAO},
∴四边形AEMF为菱形{四边相等}.