for FCPS being up-3-dimensional CollProjectiveSpace
for a, b, c, p, q, r, s being Element of FCPS st not a,b,c are_collinear & a,b,c,p are_coplanar & a,b,c,q are_coplanar & a,b,c,r are_coplanar & a,b,c,s are_coplanar holds
ex x being Element of FCPS st
( p,q,x are_collinear & r,s,x are_collinear )