Let the length of the latus rectum of an ellipse with its

Question:

Let the length of the latus rectum of an ellipse with its major axis along $x$-axis and centre at the origin, be 8 . If the distance between the foci of this ellipse is equal to the length of its minor axis, then which one of the following points lies on it?

  1. (1) $(4 \sqrt{2}, 2 \sqrt{2})$

  2. (2) $(4 \sqrt{3}, 2 \sqrt{2})$

  3. (3) $(4 \sqrt{3}, 2 \sqrt{3})$

  4. (4) $(4 \sqrt{2}, 2 \sqrt{3})$


Correct Option: , 2

Solution:

Let the ellipse be $\frac{x^{2}}{a^{2}} \frac{y^{2}}{b^{2}}=1$

Then, $\frac{2 b^{2}}{a}=8,2 a e=b^{2}$ and $b^{2}=a^{2}\left(1-e^{2}\right)$\

$\Rightarrow \quad a=8, b^{2}=32$

Then, the equation of the ellipse

$\frac{x^{2}}{64}+\frac{y^{2}}{32}=1$

Hence, the point $(4 \sqrt{3}, 2 \sqrt{2})$ lies on the ellipse.

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