theorem Th11: :: PASCAL:11

for a, b, c, d, e, f being Real
for u being non zero Element of (TOP-REAL 3)
for P being Element of (ProjectiveSpace (TOP-REAL 3)) st P = Dir u & qfconic (a,b,c,d,e,f,u) = 0 holds
P in conic (a,b,c,d,e,f)