let S be OAffinSpace; not for x, y, z being Element of S holds x,y,z is_collinear
consider x, y, z being Element of S such that
A1:
not x,y '||' x,z
by Th29;
not x,y,z is_collinear
by A1, Def5;
hence
not for x, y, z being Element of S holds x,y,z is_collinear
; verum