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Question: Answered & Verified by Expert
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?
MathematicsEllipseJEE MainJEE Main 2019 (11 Jan Shift 2)
Options:
  • A $(4 \sqrt{2}, 2 \sqrt{2})$
  • B $(4 \sqrt{3}, 2 \sqrt{2})$
  • C $(4 \sqrt{3}, 2 \sqrt{3})$
  • D $(4 \sqrt{2}, 2 \sqrt{3})$
Solution:
1615 Upvotes Verified Answer
The correct answer is: $(4 \sqrt{3}, 2 \sqrt{2})$
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 $b^{2}=a^{3}\left(1-e^{2}\right)$

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

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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