Hints:
1. You have the _center_ , therefore you actually have _two_ foci (and two tangents).
2. Mirroring a focus across a tangent gives a point at distance $2a$ from the other focus.
Hints:
1. You have the _center_ , therefore you actually have _two_ foci (and two tangents).
2. Mirroring a focus across a tangent gives a point at distance $2a$ from the other focus.