theorem Th2: :: EUCLID:32
  a*(0*n) = 0*n
proof
  |.a*(0*n).| = |.a.|*|.0*n.| by EUCLID:11
    .= |.a.|*0 by EUCLID:7
    .= 0;
  hence thesis by EUCLID:8;
end;
