
theorem Th9:
  for L be sup-Semilattice for a,b,c being Element of L holds a <=
  c & b <= c implies a"\/"b <= c
proof
  let L be sup-Semilattice;
  let a,b,c be Element of L;
  assume that
A1: a <= c and
A2: b <= c;
  c "\/" b = c by A2,Th8;
  hence thesis by A1,Th7;
end;
