
theorem Th10:
  for L be Semilattice for a,b be Element of L holds b <= a implies a"/\"b = b
proof
  let L be Semilattice;
  let a,b be Element of L;
  assume b <= a;
  then b "/\" b <= a "/\" b by Th6;
  then a"/\"b <= b & b <= a "/\" b by Th2,YELLOW_0:23;
  hence thesis by YELLOW_0:def 3;
end;
