theorem Th29: :: ANPROJ11:29

for P being non zero_proj3 Element of (ProjectiveSpace (TOP-REAL 3))
for u being non zero Element of (TOP-REAL 3)
for v being Element of (TOP-REAL 3) st u = normalize_proj3 P holds
|{(dir3a P),(dir3b P),v}| = |(u,v)|