reserve x for set;

theorem Th6:
  for L being LATTICE for a,b,c being Element of L holds
  (a"/\"b)"\/"(a"/\"c) <= a"/\"(b"\/"c)
proof
  let L be LATTICE;
  let a,b,c be Element of L;
A1: a <= a;
  c <= b"\/"c by YELLOW_0:22;
  then
A2: a"/\"c <= a"/\"(b"\/"c) by A1,YELLOW_3:2;
  b <= b"\/"c by YELLOW_0:22;
  then a"/\"b <= a"/\"(b"\/"c) by A1,YELLOW_3:2;
  hence thesis by A2,YELLOW_5:9;
end;
