reserve L for Boolean non empty RelStr;
reserve a,b,c,d for Element of L;

theorem
  (a\b)"/\"b = Bottom L
proof
  thus (a\b)"/\"b = a"/\"('not' b"/\"b) by LATTICE3:16
    .= a"/\"Bottom L by Th34
    .= Bottom L by WAYBEL_1:3;
end;
