如图,正方形ABCD的边长为2 5 ,E为AB中点,∴AE= 1 2 AD= 5 .设CM的长为x.在Rt△MNC中∵MN= 5 ,∴NC= 5?x2 ,①当Rt△AED∽Rt△CMN时,则 AE CM = AD CN ,即 5 x = 2 5 5?x2 ,解得x=1或x=-1(不合题意,舍去),②当Rt△AED∽Rt△CNM时,则