for AS being AffinSpace
for x, y being Element of the Points of (ProjHorizon AS)
for X being Element of the Lines of (IncProjSp_of AS) st x <> y & [x,X] in the Inc of (IncProjSp_of AS) & [y,X] in the Inc of (IncProjSp_of AS) holds
ex Y being Element of the Lines of (ProjHorizon AS) st X = [Y,2]