reserve T,U for non empty TopSpace;
reserve t for Point of T;
reserve n for Nat;
reserve T for TopStruct;
reserve f for PartFunc of R^1, T;
reserve c for Curve of T;

theorem Th21:
  {} is Curve of T
  proof
    reconsider f = {} as parametrized-curve PartFunc of R^1, T
    by Lm1,XBOOLE_1:2;
    f is Curve of T by Th20;
    hence thesis;
  end;
