reserve n for Nat;

theorem
  for G be Go-board for j,k,j1,k1 be Nat st 1 <= j & j <= j1
& j1 <= k1 & k1 <= k & k <= width G holds LSeg(G*(Center G,j1),G*(Center G,k1))
  c= LSeg(G*(Center G,j),G*(Center G,k))
proof
  let G be Go-board;
  let j,k,j1,k1 be Nat;
  assume that
A1: 1 <= j and
A2: j <= j1 and
A3: j1 <= k1 and
A4: k1 <= k and
A5: k <= width G;
A6: Center G <= len G by JORDAN1B:13;
  1 <= Center G by JORDAN1B:11;
  hence thesis by A1,A2,A3,A4,A5,A6,Th5;
end;
