Let C be the circle of minimum area enclosing the ellipse E:a2x2+b2y2=1 with eccentricity 21 and foci (±2,0). Let PQR be a variable triangle, whose vertex P is on the circle C and the side QR of length 2a is parallel to the major axis of E and contains the point of intersection of E with the negative y-axis. Then the maximum area of the triangle PQR is :
(A)6(3+2)
(B)8(3+2)
(C)6(2+3)
(D)8(2+3)✓ Correct
Answer: (D)
Solution
With eccentricity 21 and foci (±2,0), ae=2 gives a=4, and b2=a2(1−e2)=12, so b=23. The smallest circle enclosing the ellipse has radius a=4, centred at the origin. The base QR has length 2a=8 and lies on the horizontal line through (0,−b)=(0,−23), while the apex P lies on the circle. The greatest height from P to this line is attained at the top of the circle, a+b=4+23. The maximum area is 21⋅2a⋅(a+b)=4(4+23), which equals 8(2+3).
JEE Main · 2025 · 03 Apr 2025 · Shift 2 · Single correct option