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
  i in Seg width G & width G > 1 & n in dom G & m in Seg width
  DelCol(G,i) implies DelCol(G,i)*(n,m)=Del(Line(G,n),i).m by MATRIX_0:66;
