
theorem Th16:
  for D being non empty set,f,g being FinSequence of D holds
  len ovlpart(f,g)<=len f & len ovlpart(f,g)<=len g
proof
  let D be non empty set,f,g be FinSequence of D;
  now
    assume
A1: len ovlpart(f,g)>len f;
    ovlpart(f,g)=smid(f,len f-'len ovlpart(f,g) +1,len f) by Def2
      .=smid(f,0+1,len f) by A1,NAT_2:8
      .=f by Th6;
    hence contradiction by A1;
  end;
  hence thesis by Def2;
end;
