PS+PS′=2×32
b2=a2(1−e2)⇒9=18(1−e2)
⇒e=21
Directrix x=ea=2132=6
PS⋅PS′=21(32cosθ−6)21(32cosθ+6)
=2118cos2θ−36
(PS⋅PS′)max=18;(PS⋅PS)min=9
sum =27
If S and S′ are the foci of the ellipse 18x2+9y2=1 and P be a point on the ellipse, then min(SP.S′P)+ max(SP.S′P) is equal to :
Held on 2 Apr 2025 · Verified 6 Jul 2026.
3(1+2)
3(6+2)
9
27
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