If the distance between the foci of an ellipse is half the length of its latus rectum, then the eccentricity…

If the distance between the foci of an ellipse is half the length of its latus rectum, then the eccentricity of the ellipse is:
  1. 12
  2. 2-1
  3. 2-12
  4. 22-12

Solution

2ae=12×2b2a

2e=b2a2

We know that

e=1-b2a2

e=1-2e

e2=1-2e

e2+2e-1=0

-2±4+42=-2±222

-1+2  & -1-2

   e=2-1

Asked in: JEE Main 2015 (11 Apr Online)

Practice more Conic Sections questions on Aicharya