EllipseHardBloom L3

Question

If normal at any point $P$ to the ellipse $\frac{x^{2}}{a^{2}} + \frac{y^{2}}{b^{2}} = 1(a > b)$ meet the axes at $M$ and $N$ so that $\frac{PM}{PN} = \frac{2}{3}$, then the value of eccentricity is:

Options

A.$\frac{1}{\sqrt{2}}$
B.$\frac{\sqrt{2}}{\sqrt{3}}$
C.$\frac{1}{\sqrt{3}}$
D.none of these

Solution

Sol.(c) $(PM)^{2} = a^{2}\cos^{2}\theta\left( 1 - e^{2} \right)^{2} + b^{2}\sin^{2}\theta\ = b^{2}\left( 1 - e^{2}\cos^{2}\theta \right)$

$$\begin{matrix} & \\ (PN)^{2} = & a^{2}\cos^{2}\theta + \frac{\sin^{2}\theta}{b^{2}}\left( b^{2} + a^{2}e^{2} \right)^{2} \\ = & \frac{a^{4}}{b^{2}}\left( 1 - e^{2}\cos^{2}\theta \right) \end{matrix}$$

Create a free account to view solution

View Solution Free
Topic: EllipseยทPractice all Ellipse questions

More Ellipse Questions