theorem Th78:
  for F being Function of [:D,D9:],E, f being Function of C,D,
      g being Function of C9,D9 holds F*(f,g) is Function of [:C,C9:],E
proof
  let F be Function of [:D,D9:],E, f be Function of C,D, g be Function of C9,
  D9;
  F*(f,g) = F*[:f,g:];
  hence thesis;
end;
