Applications Of Derivatives Question 409

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

[AIEEE 2005]

Options:

A) $ \sqrt{ab} $

B) $ \frac{a}{b} $

C) $ 2ab $

D) $ ab $

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Answer:

Correct Answer: C

Solution:

Area of rectangle ABCD = $ (2a\cos \theta ) $ . $ (2b\sin \theta )=2ab\sin 2\theta $

Hence, area of greatest rectangle is equal to $ 2ab $ , when $ \sin 2\theta =1 $ .