△ADF≌△BAC
∠ADF=∠BAC
BC=AF
∠F=∠ACB
∠BAD=∠CAE=90°
∠DAE+∠BAC=180°
∠DAE+∠ADF=180°
DF∥AE
∠F=∠NAE
∠NAE=∠ACB
M、N分别是BC、DE的中点
N为AF中点
CM=AN
AC=AE
△ACM≌△EAN
∠AMC+∠MCE+∠CEN=∠AMC+∠ACM+∠ACE+∠CEA+∠AEN
∠ACE+∠CEA=90°
∠AEN=∠CAM
∠AMC+∠ACM+∠CAM=180°
∠AMC+∠MCE+∠CEN==270°
延长MA至与DE相交于G,∠MFE=90°