and
on a
common screen using the domain
Solution: The graph confirms that there is an intersecting curve:
As for the projection on the xy-plane:
Thus the parametric equations for the curve of intersection are
The projection of the curve on the xy-plane is (x,y,0) where x and y are as above.
For such (x,y) we have 
so the projection is an ellipse.
by: gm