Area of the greatest rectangle that can be inscribed in the ellipse $\frac{x^2}{a^2}+\frac{y^2}{b^2}=1$ is
- $2 a b$
- $a b$
- $3a b$
- $\frac{a}{b}$
Solution

Area of rectangle $A B C D=(2 a\cos \theta)$ $(2 b \sin \theta)=2 a b \sin 2 \theta$ $\Rightarrow$ Area of greatest rectangle is equal to $2 a b$ when $\sin 2 \theta=1$.
Asked in: JEE Main 2005
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