∵DE=CF,OD=OC∴OE=OF在△AOE与△DOF中OA=OD﹛∠AOD=∠COD OE=OF∴△AOE≌△DOF（SAS）∴∠OAE=∠ODF∵∠OAE+∠OMF+∠AFD=180?稀螼DF+∠DOC+∠OFD=180?蟗r>∴∠AMF=∠DOC∵∠DOC=90?喜葡哅F=90?哹r>∴AM⊥DF
