Question:
Find the equation of the hyperbola whose foci are $(\pm \sqrt{5} 0)$ and the eccentricity is $\sqrt{\frac{5}{3}}$.
Solution:
Given: Foci are $(\pm \sqrt{5}, 0)$, and the eccentricity is $\sqrt{\frac{5}{3}}$
Need to find: The equation of the hyperbola.
Let, the equation of the hyperbola be: $\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1$
The eccentricity, $\mathrm{e}=\sqrt{\frac{5}{3}}$
And also given, foci are $(\pm \sqrt{5}, 0)$
That means, ae $=\sqrt{5}$
$\Rightarrow a=\frac{\sqrt{5}}{e}$
$\Rightarrow a=\frac{\sqrt{5}}{\sqrt{\frac{5}{3}}}\left[\right.$ As $\left.e=\sqrt{\frac{5}{3}}\right]$
$\Rightarrow a=\sqrt{3}$
We know that, $e=\sqrt{1+\frac{b^{2}}{a^{2}}}$
Therefore,