theorem Th1:
  [1,1] in [:Seg 3,Seg 3:] & [1,2] in [:Seg 3,Seg 3:] &
  [1,3] in [:Seg 3,Seg 3:] & [2,1] in [:Seg 3,Seg 3:] &
  [2,2] in [:Seg 3,Seg 3:] & [2,3] in [:Seg 3,Seg 3:] &
  [3,1] in [:Seg 3,Seg 3:] & [3,2] in [:Seg 3,Seg 3:] &
  [3,3] in [:Seg 3,Seg 3:]
  proof
    1 in Seg 3 & 2 in Seg 3 & 3 in Seg 3 by FINSEQ_1:1;
    hence thesis by ZFMISC_1:87;
  end;
