theorem
  |(<e3>,<e3>)| = 1
proof
  <e3>.1 = 0 & <e3>.2 = 0 & <e3>.3 = 1;
  then |(<e3>,<e3>)| = 0 * 0 + 0 * 0 + 1 * 1 by Lm5
  .= 1;
  hence thesis;
end;
