 reserve U for set,
         X, Y for Subset of U;
 reserve U for non empty set,
         A, B, C for non empty IntervalSet of U;

theorem Th35:
  A _/\_ (A _\/_ B) = A
  proof
    A is non empty ordered Subset-Family of U &
      B is non empty ordered Subset-Family of U by Lm4;
    hence thesis by Th33;
 end;
