theorem Th6: :: PROJDES1:6

for FCPS being up-3-dimensional CollProjectiveSpace
for a, b, c, d being Element of FCPS st ( a,b,c are_collinear or b,c,d are_collinear or c,d,a are_collinear or d,a,b are_collinear ) holds
a,b,c,d are_coplanar