
theorem
  for f be heterogeneous non empty real-valued FinSequence holds
    Het f >= 2
  proof
    let f be heterogeneous non empty real-valued FinSequence;
    set x = the Element of MeanLess f;
    set y = the Element of MeanMore f;
    HetSet f = MeanLess f \/ MeanMore f by MeanSum; then
A0: x in HetSet f & y in HetSet f by XBOOLE_0:def 3;
A4: x <> y by XBOOLE_0:3,MeanMiss;
A5: card {x,y} = 2 by CARD_2:57,A4;
    card Segm 2 c= card Segm Het f by A5,ZFMISC_1:32,A0,CARD_1:11;
    hence thesis by NAT_1:40;
  end;
