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GATE 2020 AE – Question 8

General Aptitude · Quantitative Aptitude: Algebra, Geometry and Mensuration · 2 marks · Multiple choice

A rectangle PQRS of maximum possible area is inscribed in a circle of centre O and radius a as shown. Find the shaded area outside the rectangle and inside the circle.

Diagram for GATE 2020 AE question 8
  1. $\pi a^2-a^2$
  2. $\pi a^2-\sqrt2a^2$
  3. $\pi a^2-2a^2$
  4. $\pi a^2-3a^2$

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Show answer and explanation

Correct answer: (C) $\pi a^2-2a^2$

Explanation

The rectangle has diagonal 2a, so side lengths x,y satisfy $x^2+y^2=4a^2$. Since $2xy\le x^2+y^2$, its maximum area is 2a², attained by a square. Subtract from the circle area πa² to obtain πa²−2a², C.

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