
theorem
  for L be Semilattice for x,y be Element of L holds "\/"((downarrow x)
  /\ (downarrow y),L) = x "/\" y
proof
  let L be Semilattice;
  let x,y be Element of L;
  (downarrow x) /\ (downarrow y) = downarrow (x "/\" y) by WAYBEL14:3;
  hence thesis by WAYBEL_0:34;
end;
