Conic Sections Question 193

Question: If the eccentricity of an ellipse be 5/8 and the distance between its foci be 10, then its latus rectum is

Options:

A) 39/4

B) 12

C) 15

D) 37/2

Show Answer

Answer:

Correct Answer: A

Solution:

$ a=\frac{10}{\frac{2.5}{8}}=8 $ , $ b=8\sqrt{1-\frac{25}{64}}=8\frac{\sqrt{39}}{8} $

Latus rectum $ =\frac{2b^{2}}{a}=\frac{2\times 39}{8}=\frac{39}{4} $ .