reserve n,m for Nat;
reserve p,q,r for Element of Nat_Lattice;
reserve p,q,r for Element of Nat_Lattice;

theorem Th5:
  lcmlat.(p,q)=lcmlat.(q,p)
proof
  thus lcmlat.(p,q)=q"\/"p by LATTICES:def 1
    .=lcmlat.(q,p);
end;
