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10-2. Parabola, Ellipse, Hyperbola
hard

माना त्रिज्या $4$ का एक वृत्त तथा दीर्घवृत्त $15 \mathrm{x}^2+19 \mathrm{y}^2=285$ संकेन्द्री है, तो उभयनिष्ठ स्पर्श रेखाएँ दीर्घवृत्त के लघु अक्ष से कौन सा कोण बनाती है?ined to the minor axis of the ellipse at the angle.

A

$\frac{\pi}{4}$

B

$\frac{\pi}{3}$

C

$\frac{\pi}{12}$

D

$\frac{\pi}{6}$

(JEE MAIN-2023)

Solution

$\frac{x^2}{19}+\frac{y^2}{15}=1$

Let tang be

$y = mx \pm \sqrt{19 m^2+15}$

$mx – y \pm \sqrt{19 m^2+15}=0$

Parallel from $(0,0)=4$

$\left|\frac{ \pm \sqrt{19 m ^2+15}}{\sqrt{ m ^2+1}}\right|=4$

$19 m ^2+15=16 m ^2+16$

$3 m ^2=1$

$m = \pm \frac{1}{\sqrt{3}}$

$\theta=\frac{\pi}{6} \text { with } x \text {-axis }$

Required angle $\frac{\pi}{3}$.

Standard 11
Mathematics

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