
theorem Th33:
  id NAT is sequence of ExtREAL &
  id NAT is one-to-one & NAT = rng id NAT &
  rng id NAT is non empty Subset of ExtREAL
proof
  NAT c= ExtREAL by NUMBERS:19,31;
  then reconsider F = id NAT as sequence of ExtREAL by FUNCT_2:7;
  rng F c= ExtREAL;
  hence thesis;
end;
