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JEE Main 2024
Conic Sections
Ellipse
Medium

Question

Let the tangents at the points P\mathrm{P} and Q\mathrm{Q} on the ellipse x22+y24=1\frac{x^{2}}{2}+\frac{y^{2}}{4}=1 meet at the point R(2,222)R(\sqrt{2}, 2 \sqrt{2}-2). If S\mathrm{S} is the focus of the ellipse on its negative major axis, then SP2+SQ2\mathrm{SP}^{2}+\mathrm{SQ}^{2} is equal to ___________.

Answer: 2

Solution

This problem combines several key concepts of ellipses: identifying its standard form, calculating its foci and eccentricity, understanding the equation of a chord of contact, and applying the focal distance property. Our goal is to find the sum of the squared distances from a specific focus to the points of tangency.


1. Analyze the Ellipse and its Properties

First, let's identify the characteristics of the given ellipse: The equation is x22+y24=1\frac{x^{2}}{2}+\frac{y^{2}}{4}=1.

  • Standard Form: Compare this to the standard form of an ellipse x2b2+y2a2=1\frac{x^2}{b^2} + \frac{y^2}{a^2} = 1 (for a vertical major axis) or

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