reserve i,j,k,l,m,n for Nat,
  D for non empty set,
  f for FinSequence of D;
reserve X for compact Subset of TOP-REAL 2;
reserve r for Real;

theorem
  for f being non trivial FinSequence of TOP-REAL 2 for i,j st i in dom
  f & j in dom f holds mid(f,i,j) is_in_the_area_of f by Th21,Th22;
