延长CB至E,使BE=DN,又AD=AB,ADN=ABE=90,△ADN≌△ABE,故AN=AE,DAN=BAE,
MAN=45,DAB=90推得DAN+MAB=45
而DAN=BAE,故MAE=MAB+BAE=45=MAN,AN=AE,AM=AM,△AMN≌△AME,MN=ME=MB+BE=MB+DN
延长CB至E,使BE=DN,又AD=AB,ADN=ABE=90,△ADN≌△ABE,故AN=AE,DAN=BAE,
MAN=45,DAB=90推得DAN+MAB=45
而DAN=BAE,故MAE=MAB+BAE=45=MAN,AN=AE,AM=AM,△AMN≌△AME,MN=ME=MB+BE=MB+DN