
theorem Th23:
  for L being antisymmetric with_infima RelStr for a,b,c being
Element of L holds c = a"/\"b iff c <= a & c <= b & for d being Element of L st
  d <= a & d <= b holds c >= d
proof
  let A be antisymmetric with_infima RelStr;
  let a,b be Element of A;
  ex x being Element of A st a >= x & b >= x & for c being Element of A st
  a >= c & b >= c holds x >= c by LATTICE3:def 11;
  hence thesis by LATTICE3:def 14;
end;
