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 Th13:
  width G = m+1 & m>0 & k in Seg m & n in dom G implies k in Seg
  width G & DelCol(G,width G)*(n,k) = G*(n,k) & width G in Seg width G
     by MATRIX_0:74;
