theorem Th23: :: SEMI_AF1:23

for SAS being Semi_Affine_Space
for a, b, c, p, q, r being Element of SAS st not a,b,c are_collinear & a,b // p,q & a,c // p,r & p <> q & p <> r holds
not p,q,r are_collinear by Th15;