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JEE Advanced · Mathematics · 14. Ellipse

Define the collections E1,E2,E3,.... of ellipses and R1,R2,R3,.... of rectangles as follows:
E1:x29+y24=1;
R1: rectangle of largest area, with sides parallel to the axes, inscribed in E1;
En: ellipse x2an2+y2bn2=1 of largest area inscribed in Rn-1,n>1;
Rn: rectangle of largest area, with sides parallel to the axes, inscribed in En,n>1.
Then which of the following options is/are correct?

  1. A The eccentricities of E18 and E19 are NOT equal
  2. B The distance of a focus from the centre in E9 is 532
  3. C The length of latus rectum of E9 is 16
  4. D n=1NareaofRn<24, for each positive integer N
Verified Solution

Answer & Solution

Correct Answer

(D) n=1NareaofRn<24, for each positive integer N

Step-by-step Solution

Detailed explanation

As given:
E1=x2a2+y2b2=1 (Here a=3 and b=2 )
Semi major axis =a and semi minor axis =b
Let a vertex of R1 be acosθ,bsinθ
Then area of R1=2acosθ×2bsinθ
R1=2absin2θ
Maximum area of R1=2ab, when sin2θ=1
or, 2θ=π2
θ=π4
Maximum area of R1=2ab ....(i)

Now, ellipse E2 will have semi major axis a2 and semi minor axis b2
E2=x2a22+y2b22=1,
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