Gujarati
Hindi
10-2. Parabola, Ellipse, Hyperbola
normal

If area of quadrilateral formed by tangents  drawn at ends of latus rectum of hyperbola $\frac{x^2}{a^2}-\frac{y^2}{b^2}=1$ is equal to square of distance between centre and one  focus of hyperbola, then $e^3$ is ($e$ is eccentricity of hyperbola)

A

$2\sqrt 2$

B

$2$

C

$3$

D

$8$

Solution

ends of $L.R$ $\left(\pm a e, \pm \frac{b^{2}}{a}\right)$

$\Rightarrow$ tan gents are $\pm \frac{\mathrm{e}}{\mathrm{a}} \mathrm{x} \pm \frac{1}{\mathrm{a}} \mathrm{y}=1$

$\Rightarrow$ Area $=\frac{2 a^{2}}{e}-a^{2} e^{2}$

$\Rightarrow \mathrm{e}^{3}=2$

Standard 11
Mathematics

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