let AS be AffinSpace; :: thesis: for a, b, c, d, p being POINT of (IncProjSp_of AS)
for M, N, P, Q being LINE of (IncProjSp_of AS) st a on M & b on M & c on N & d on N & p on M & p on N & a on P & c on P & b on Q & d on Q & not p on P & not p on Q & M <> N & p is not Element of AS & ( a is Element of AS or b is Element of AS or c is Element of AS or d is Element of AS ) holds
ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q )

let a, b, c, d, p be POINT of (IncProjSp_of AS); :: thesis: for M, N, P, Q being LINE of (IncProjSp_of AS) st a on M & b on M & c on N & d on N & p on M & p on N & a on P & c on P & b on Q & d on Q & not p on P & not p on Q & M <> N & p is not Element of AS & ( a is Element of AS or b is Element of AS or c is Element of AS or d is Element of AS ) holds
ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q )

let M, N, P, Q be LINE of (IncProjSp_of AS); :: thesis: ( a on M & b on M & c on N & d on N & p on M & p on N & a on P & c on P & b on Q & d on Q & not p on P & not p on Q & M <> N & p is not Element of AS & ( a is Element of AS or b is Element of AS or c is Element of AS or d is Element of AS ) implies ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q ) )

assume that
A1: a on M and
A2: b on M and
A3: c on N and
A4: d on N and
A5: p on M and
A6: p on N and
A7: a on P and
A8: c on P and
A9: b on Q and
A10: d on Q and
A11: not p on P and
A12: not p on Q and
A13: M <> N and
A14: p is not Element of AS and
A15: ( a is Element of AS or b is Element of AS or c is Element of AS or d is Element of AS ) ; :: thesis: ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q )

now :: thesis: ( ( b is Element of AS or d is Element of AS ) implies ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q ) )
assume ( b is Element of AS or d is Element of AS ) ; :: thesis: ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q )

then ex q being POINT of (IncProjSp_of AS) st
( q on Q & q on P ) by A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, Lm10;
hence ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q ) ; :: thesis: verum
end;
hence ex q being POINT of (IncProjSp_of AS) st
( q on P & q on Q ) by A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, Lm10; :: thesis: verum