连接AD.
已知,DN是AB的中垂线,可得：DA = DB ,∠DAB = ∠B = 22.5° ；
因为,∠ADE = ∠DAB+∠B = 45° ,∠AED = 90° ,
所以,△ADE是等腰直角三角形,可得：DE = AE .
在△DEM和△AEC中,∠MDE = 90°-∠C = ∠CAE ,DE = AE ,∠DEM = 90°= ∠AEC ,
所以,△DEM ≌ △AEC ,
可得：EM = EC .