theorem Th22:
for
SAS being
Semi_Affine_Space for
a1,
a2,
a3 being
Element of
SAS st
a1,
a2,
a3 are_collinear holds
(
a1,
a3,
a2 are_collinear &
a2,
a1,
a3 are_collinear &
a2,
a3,
a1 are_collinear &
a3,
a1,
a2 are_collinear &
a3,
a2,
a1 are_collinear )
by Th7;