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Conic Sections
Parabola
Medium

Question

Let PQ be a focal chord of the parabola y 2 = 4x such that it subtends an angle of π2{\pi \over 2} at the point (3, 0). Let the line segment PQ be also a focal chord of the ellipse E:x2a2+y2b2=1E:{{{x^2}} \over {{a^2}}} + {{{y^2}} \over {{b^2}}} = 1, a2>b2{a^2} > {b^2}. If e is the eccentricity of the ellipse E, then the value of 1e2{1 \over {{e^2}}} is equal to :

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Solution

This problem is an excellent test of your understanding of conic sections, specifically parabolas and ellipses, and how to apply their properties in a coordinated manner. We will break down the problem into logical steps, focusing on defining and utilizing key concepts.


1. Understanding the Parabola and its Focal Chord

The given parabola is y2=4xy^2 = 4x.

Key Concept: The standard equation of a parabola is y2=4axy^2 = 4ax. Its focus is at S(a,0)S(a,0) and its directrix is x=ax = -a. By comparing y2=4xy^2 = 4x with y2=4axy^2 = 4ax, we identify a=1a=1. Therefore, the focus of this parabola is $S(

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