Question

If the distance from the directrix is greater than the distance from the focus then what is the name of the conic section?

(a) Hyperbola

(b) Parabola

(c) Ellipse

(d) Circle

The question was asked by my college professor while I was bunking the class.

This intriguing question comes from Basics of Conic Sections in division Curves used in Engineering Practice of Engineering Drawing

Answer 1

Correct choice is (c) Ellipse

For explanation I would say: Eccentricity is defined as the ratio of the distance from the focus to the distance from the directrix and it is denoted by e. Therefore, by definition the value of eccentricity is less than one hence the conic section is an ellipse.