Q. If the eccentricity of the two ellipse $\frac{x^{2}}{169} + \frac{y^{2}}{25} = 1$ and $\frac{x^{2}}{a^{2}} + \frac{y^{2}}{b^{2}} = 1$ are equal, then the value of $\frac{a}{b}$ is

A) $\frac{5}{13}$
B) $\frac{6}{13}$
C) $\frac{13}{5}$
D) $\frac{13}{6}$
Explanation

(c)
Equation of the ellipse are $\frac{x^{2}}{13^{2}} + \frac{y^{2}}{5^{2}} = 1$ and $\frac{x^{2}}{a^{2}} + \frac{y^{2}}{b^{2}} = 1$ and their eccentricity are
$e = \sqrt{1 - \frac{25}{169}}$ and $e^{'} = \sqrt{1 - \frac{b^{2}}{a^{2}}}$
According to given condition, $e^{'} = e$
$\Rightarrow \sqrt{1 - \left( \frac{b^{2}}{a^{2}} \right)} = \sqrt{1 - \left( \frac{25}{169} \right)}$
$\Rightarrow \frac{b}{a} = \frac{5}{13}$ $(\because a > 0,\ b > 0)$
$\Rightarrow \frac{a}{b} = \frac{13}{5}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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