Definite Integration Question 500

Question: The sine and cosine curves intersects infinitely many times giving bounded regions of equal areas. The area of one of such region is

[DCE 2005]

Options:

A) $ \sqrt{2} $

B) $ 2\sqrt{2} $

C) $ 3\sqrt{2} $

D) $ 4\sqrt{2} $

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Answer:

Correct Answer: B

Solution:

Point of intersection of y=sinx and $ y=\cos x $ are $ \frac{\pi }{4}, $

$ \frac{\pi }{4},\frac{5\pi }{4} $ .
Since, $ \sin x\ge \cos x $ on the interval $ [ \frac{\pi }{4},\frac{5\pi }{4} ] $
$ \therefore $ Area of one such region $ =\int _{\pi /4}^{5\pi /4}{(\sin x-\cos x)\ dx} $

$ =2\sqrt{2}sq.\ unit $ .