reserve x,y for Real;
reserve a,b,c for Element of Real_Lattice;
reserve p,q,r for Element of Real_Lattice;

theorem Th2:
  minreal.(p,q) = minreal.(q,p)
proof
  thus minreal.(p,q) = q"/\"p by LATTICES:def 2
    .= minreal.(q,p);
end;
