证明：∵∠DAB=∠EAC∴∠DAB+∠BAC=∠EAC+∠BAC即∠DAC=∠BAE∵AD=AE，AB=AC∴△DAC≌△BAE∴∠D=∠E∵∠DAM=∠EAN，AD=AE∴△ADM≌△AEN∴AM=AN
