Desargues's Theorem
Desargues:=proc() local A,B,i,m,t,s:
for i from 1 to 3 do
A[i]:=
ParamLine(m[i],0,t[i]):
B[i]:=
ParamLine(m[i],0,s[i]):
od:
Colinear
(
end:
Pt
(Le(A[1],A[2]) ,
Le(B[1],B[2])),
Pt
(Le(A[1],A[3]) ,
Le(B[1],B[3])),
Pt
(Le(A[2],A[3]) ,
Le(B[2],B[3]))
):