Let PQ be a focal chord of the parabola y^2=4x such that it subtends an angle of π 2 at the point (3,0). Let the line segment PQ be also a focal…
JEE Main 2022 — Mathematics Coordinate Geometry
2022mcqmedium
Let PQ be a focal chord of the parabola y2=4x such that it subtends an angle of 2π at the point (3,0). Let the line segment PQ be also a focal chord of the ellipse E:a2x2+b2y2=1,a2>b2. If e is the eccentricity of the ellipse E, then the value of e21 is equal to
Official previous-year question
Held on 29 Jun 2022 · Verified 6 Jul 2026.
Options
A
1+2
B
3+22
C
1+23
D
4+53
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Solution
Since PQ is focal chord of the parabola y2=4ax
so let P(t2,2t), Q(t21,−t2) and R(3,0)
Given mPR⋅mPQ=−1
t2−32t×t21−3−t2=−1
(t2−1)2=0
⇒t=1
i.e. PQ must be the latus rectum
We get P(1,2)&Q(1,-2)
For ellipse
\frac{2{b}^{2}}{a}=4&ae=1
Also b2=a2(1−e2)
∴a=1+2
ande2=3−22
Hence e21=3−221=3+22
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