reserve A,B,C,D for Category,
  F for Functor of A,B,
  G for Functor of B,C;

theorem Th2:
  for F1,F2 being Functor of A,B st F1 is_transformable_to F2 for t
being transformation of F1,F2, a being Object of A holds t.a in Hom(F1.a,F2.a)
proof
  let F1,F2 be Functor of A,B such that
A1: F1 is_transformable_to F2;
  let t be transformation of F1,F2, a be Object of A;
  Hom(F1.a,F2.a)<>{} by A1;
  hence thesis by CAT_1:def 5;
end;
