In more advanced problems on the ellipse, you will need to know the equation of the directrix and the coordinates of the focus which are given in terms of the eccentricity e. I first give you a summary of these results and then the proofs.

In more advanced problems on the ellipse, you will need to know the equation of the directrix and the coordinates of the focus which are given in terms of the eccentricity e. I first give you a summary of these results and then the proofs.