theorem Th23:
  c is parametrized-curve PartFunc of R^1, T
  proof
    c in {f where f is Element of PFuncs(REAL, [#]T) :
     f is parametrized-curve PartFunc of R^1, T};
    then consider f be Element of PFuncs(REAL, [#]T) such that
A1: c = f & f is parametrized-curve PartFunc of R^1, T;
    thus thesis by A1;
  end;
