Why directrix is taken on the major axis of ellipse. Why can't we take directrix on minor axis of ellipse ?

1 Answer
Apr 4, 2018

Please see below.

Explanation:

Major axis and minor axis of an ellipse are perpendicular to each other.

As directrix is perpendicular to major axis

and it is parallel to minor axis.

It is not taken on the major axis of ellipse or on minor axis. It only cuts major axis at a distance of #a/e# from center of ellipse, where #a# is half the major axis and #e# is its eccentricity.

https://math.tutorvista.com/geometry/directrices-of-an-ellipse.html