reserve p,q for Point of TOP-REAL 2,
  i,i1,i2,j,j1,j2,k for Nat,
  r,s for Real,
  G for Matrix of TOP-REAL 2;
reserve f for standard special_circular_sequence;

theorem Th22:
  for G being Go-board holds 1 <= i & i < len G & 1 <= j & j <= width G
  implies LSeg(G*(i,j),G*(i+1,j)) c= cell(G,i,j)
proof
  let G be Go-board;
  assume that
A1: 1 <= i and
A2: i < len G and
A3: 1 <= j and
A4: j <= width G;
A5: LSeg(G*(i,j),G*(i+1,j)) c= h_strip(G,j) by A1,A2,A3,A4,Th16;
  i+1 <= len G by A2,NAT_1:13;
  then LSeg(G*(i,j),G*(i+1,j)) c= v_strip(G,i) by A1,A3,A4,Th20;
  hence thesis by A5,XBOOLE_1:19;
end;
