theorem Th24: :: PASCAL:24

for p2, p4, p6, p7, p8 being Point of (TOP-REAL 3) st |{p2,p6,p7}| = 0 holds
|{p2,p4,p7}| * |{p2,p6,p8}| = - (|{p2,p4,p6}| * |{p2,p8,p7}|)