Given that,

∠SBS′=2π
⇒∠OBS=4π
⇒b=ae...(i)
Also, area (ΔSBS′)=8
⇒21.2ae.b=8
⇒aeb=8...(ii)
From equations (i)&(ii),
b2=8 and a2=b2+a2e2=8+8=16
⇒b=22 and a=4
Thus, the length of the latus rectum is a2b2=416=4
JEE Main 2019 — Mathematics Coordinate Geometry
Let S and S′ be the foci of an ellipse and B be any one of the extremities of its minor axis. If ΔS′BS is a right angled triangle with right angle at B and area (ΔS′BS)=8sq.units, then the length of a latus rectum of the ellipse is :
Held on 12 Jan 2019 · Verified 6 Jul 2026.
22
2
4
42
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