reserve Y for non empty set,
  G for Subset of PARTITIONS(Y),
  A,B,C,D,E,F for a_partition of Y;

theorem Th5:
  G={A,B,C} & A<>B & B<>C implies CompF(B,G) = C '/\' A
proof
  {A,B,C} = {B,C,A} by ENUMSET1:59;
  hence thesis by Th4;
end;
