theorem Th37:
  |.<*> A.| = A --> 0
proof
A1: now
    let x be object;
    assume x in A;
    then reconsider a = x as Element of A;
    thus |.<*>A.|.x = card dom ({a}|`{}) by Def7
      .= 0 by CARD_1:27,RELAT_1:38,107;
  end;
  dom |.<*>A.| = A by Th28;
  hence thesis by A1,FUNCOP_1:11;
end;
