theorem Th64:
  for T being (Functor of C,D), f being Morphism of C holds (Obj
  T).(dom f) = dom (T.f) & (Obj T).(cod f) = cod (T.f)
proof
  let T be (Functor of C,D), f be Morphism of C;
  T.(id dom f) = id dom (T.f) & T.(id cod f) = id cod (T.f)
          by Def19;
  hence thesis by Th62;
end;
