Engler — TJie Normal to the Conic Section. 149 



t Ni; 



Figure 6. 



any point in the plane on the convex side (or within) the 

 evolute (Fig. 7), both branches of the hyperbola cut the 

 ellipse, each in two points, and there are four normals, P^ST^, 

 PN,, PN., PJSFi ; and for any point in the plane on the con- 



FlGURE 7. 



