reserve i, i1, i2, j, j1, j2, k, m, n, t for Nat,
  D for non empty Subset of TOP-REAL 2,
  E for compact non vertical non horizontal Subset of TOP-REAL 2,
  C for compact connected non vertical non horizontal Subset of TOP-REAL 2,
  G for Go-board,
  p, q, x for Point of TOP-REAL 2,
  r, s for Real;

theorem Th8:
  p in Vertical_Line(p`1)
proof
  p in {q where q is Point of TOP-REAL 2: p`1=q`1};
  hence thesis by JORDAN6:def 6;
end;
