reserve p for Point of TOP-REAL 2,
  f,f1,f2,g for FinSequence of TOP-REAL 2,
  v, v1,v2 for FinSequence of REAL,
  r,s for Real,
  n,m,i,j,k for Nat,
  x for set;
reserve G for Go-board;

theorem
  rng f misses rng Col(G,i) & f/.n in rng Line(G,m) & n in dom f & i in
  Seg width G & m in dom G & width G>1 implies f/.n in rng Line(DelCol(G,i),m)
     by MATRIX_0:75;
