EllipseHardBloom L3

Question

The angle between ellipse $\frac{x^{2}}{4} + y^{2} = 1$ and circle $x^{2} + y^{2} = 2$ is $\theta$, then $tan\theta$ is equal to:

Options

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

Solution

Sol.(b) Equation of normal to ellipse at $P$ is

$$\frac{4x}{2/\sqrt{3}} - \frac{y}{\sqrt{2}/\sqrt{3}} = 3$$

$$\Rightarrow 2x - \frac{y}{\sqrt{2}} = \sqrt{3} $$

⇒ slope of normal to ellipse at $P = m_{1} = 2\sqrt{2}$

Slope of normal to circle at

$$\begin{matrix} P = m_{2} = \frac{\frac{\sqrt{2}}{\sqrt{3}} - 0}{\frac{2}{\sqrt{3}} - 0} = \frac{1}{\sqrt{2}} \\ tan\theta = \frac{2\sqrt{2} - \frac{1}{\sqrt{2}}}{1 + 2\sqrt{2}\frac{1}{\sqrt{2}}} = \frac{3}{3\sqrt{2}} = \frac{1}{\sqrt{2}} \end{matrix}$$

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