reserve p,q,r for FinSequence;
reserve u,v,x,y,y1,y2,z for object, A,D,X,Y for set;
reserve i,j,k,l,m,n for Nat;

theorem
  rng p <> {} implies 1 in dom p
proof
  set y = the Element of rng p;
  assume rng p <> {};
  then y in rng p;
  hence thesis by Th29;
end;
