for p, p1, p2, q being Point of (TOP-REAL 2) st not q in LSeg (p1,p2) & p in LSeg (p1,p2) & p <> p1 & p <> p2 & ( ( p1 `1 = p2 `1 & p2 `1 = q `1 ) or ( p1 `2 = p2 `2 & p2 `2 = q `2 ) ) & not p1 in LSeg (q,p) holds
p2 in LSeg (q,p)