  Both the ellipse and the hyperbola are geometric places that can be defined
by establishing a relationship between points $P$ of the plane and two fixed
points $A$ and $B$ (which are its foci $F'=A$ and $F=B$). Given two points $A$
and $B$ of the plan (which we no longer call the foci $F$ and $F'$), we are
going to present three geometric places associated with $A$ and $B$ other than
the ellipse and the hyperbola.
