The length of the latus-rectum of the ellipse, whose foci are (2, 5) and (2, -3) and eccentricity is 45, is
- 503
- 185
- 65
- 103
Answer
(2) 185
Solution
The foci lie on the line x = 2, so the major axis is vertical.
Distance between foci = 2ae = 5 - (-3) = 8 ⇒ ae = 4
∵ e = 45 ⇒ a = 5
b2 = a2(1 - e2) = 25 (1 - 1625 ) = 9
Length of latus rectum = 2b2a = 2 95 = 185
Answer: (2)