
To unravel four 2D curves producing a higher invaiant
Posted:
Jun 8, 2010 1:28 PM


Four arbitrary points ( x1,y1,h), ( x2,y2,h), ( x3,y3,h), ( x4,y4,h), are connected with the origin ( 0,0,0) forming 4 rays which are projected on the xz plane ; these projections produce a crossratio CR on any cutting transversal.
How should the projection of these four points ( x1,y1) ,... (x4,y4) move on the xy plane so that the CR does not change? That is, what are coordinates of the quadrilateral vertices as a function of an arbitrary parameter t ?
Is it possible to show these on GSP?
Best Regards, Narasimham

