theorem
  |(<e1>,<e1>)| = 1
proof
  <e1>.1 = 1 & <e1>.2 = 0 & <e1>.3 = 0;
  then |(<e1>,<e1>)| = 1 * 1 + 0 * 0 + 0 * 0 by Lm5
  .= 1;
  hence thesis;
end;
