theorem Th14:
  (a*x).|.y = x.|.((a*')*y)
proof
  (a*x) .|. y = a * x .|. y by Def11
    .= (a*')*' * (y.|.x)*' by Def11
    .= ((a*')*(y.|.x))*' by COMPLEX1:35
    .= (((a*')*y).|.x)*' by Def11;
  hence thesis by Def11;
end;
