theorem Th10: :: ANPROJ10:17

for V being RealLinearSpace
for P, Q, R being Element of V st P,Q,R are_collinear & P <> R & Q <> R & P <> Q holds
affine-ratio (Q,P,R) = (affine-ratio (P,Q,R)) / ((affine-ratio (P,Q,R)) - 1)