reserve X1,X2,X3,X4 for set;

theorem
  ((X1 /\ X4) \ (X2 \/ X3)) misses (X1 \ (X2 \/ X3 \/ X4)) &
  ((X1 /\ X4) \ (X2 \/ X3)) misses ((X1 /\ X3 /\ X4) \ X2) &
  (X1 \ (X2 \/ X3 \/ X4)) misses ((X1 /\ X3 /\ X4) \ X2) by Thm01;
