(1)∵∠EA1O=∠MC1O=Rt∠,OA1=OC1,∠1=∠2
    ∴△OC1M≌△OA1E
(2)作OH⊥MN于H
    ∵OE=OM,∠EON=∠M0N,ON=ON,
   ∴ONM≌△ONE
     ∴∠3=∠4,又∵∠OA1N=∠OHN=Rt∠,ON=ON
    ∴OHN≌△OA1N,
  ∴OH=OA1=a
(3)∵∠OHM=∠OC1M=Rt∠,OH=OC1,OM=OM
∴OHM≌△OC1M,∴HM=C1M
p=NM+B1M+B1N
  =NH+MH+B1M+B1N
  =A1B1+B1C1
  =2a