theorem Th28: :: JORDAN3:28

for p1, p2, q1, q2 being Point of (TOP-REAL 2) st q1 in LSeg (p1,p2) & q2 in LSeg (p1,p2) & p1 <> p2 holds
( ( LE q1,q2,p1,p2 or LT q2,q1,p1,p2 ) & ( not LE q1,q2,p1,p2 or not LT q2,q1,p1,p2 ) )