theorem
  for X0 being non empty SubSpace of X holds (modid(X,X0))|X0 is
  continuous Function of X0,X modified_with_respect_to X0
proof
  let X0 be non empty SubSpace of X;
  for x0 being Point of X0 holds ((modid(X,X0))|X0) is_continuous_at x0 by
Th107;
  hence thesis by Th44;
end;
