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WBJEE · Maths · Hyperbola

\(P Q\) is a double ordinate of the hyperbola \(\frac{x^2}{a^2}-\frac{y^2}{b^2}=1\) such that \(\triangle O P Q\) is an equilateral triangle, \(O\) being the centre of the hyperbola. Then the eccentricity e of the hyperbola satisfies

  1. A \(1 < \mathrm{e} < 2 / \sqrt{3}\)
  2. B \(\mathrm{e}=2 / \sqrt{3}\)
  3. C \(\mathrm{e}=2 \sqrt{3}\)
  4. D \(\mathrm{e} > 2 / \sqrt{3}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\mathrm{e} > 2 / \sqrt{3}\)

Step-by-step Solution

Detailed explanation

\(\tan 30^{\circ}=\frac{b \tan \theta}{a \sec \theta}\) \(\Rightarrow \frac{b}{a}=\frac{1}{\sin \theta \sqrt{3}}\) \(e=\sqrt{1+\frac{1}{3 \sin ^2 \theta}} > \sqrt{1+\frac{1}{3}}\) \(\Rightarrow e > \frac{2}{\sqrt{3}}\left(0