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10-2. Parabola, Ellipse, Hyperbola
normal
The asymptote of the hyperbola $\frac{{{x^2}}}{{{a^2}}} - \frac{{{y^2}}}{{{b^2}}}= 1$ form with any tangent to the hyperbola a triangle whose area is $a^2$ $\tan$ $ \lambda $ in magnitude then its eccentricity is :
A
$\sec \lambda$
B
$ cosec\lambda$
C
$\sec^2\lambda$
D
$cosec^2\lambda$
Solution
$A = ab = a^2 \tan \lambda$
$ \Rightarrow $ $b/a = \tan \lambda ,$
hence $e^2 = 1 + (b^2/a^2) $
$\Rightarrow $ $e^2 = 1 + \tan^2 \lambda$
$ \Rightarrow$ $ e= sec \lambda$
Standard 11
Mathematics