- Home
- Standard 11
- Mathematics
10-2. Parabola, Ellipse, Hyperbola
easy
The distance between the directrices of a rectangular hyperbola is $10$ units, then distance between its foci is
A
$10\sqrt 2 $
B
$5$
C
$5\sqrt 2 $
D
$20$
Solution
(d) Distance between directrices $ = \frac{{2a}}{e}$.
Eccentricity of rectangular hyperbola $ = \sqrt 2 $.
Distance between directrics $ = \frac{{2a}}{{\sqrt 2 }}$.
Given that , $\frac{{2a}}{{\sqrt 2 }} = 10$
==> $2a = 10\sqrt 2 $
Now, distance between foci $ = 2ae = (10\sqrt 2 )\,(\sqrt 2 ) = 20.$
Standard 11
Mathematics