Differentiation Question 451

Question: The differential equation satisfied by the function $ y=\sqrt{\sin x+\sqrt{\sin x+\sqrt{\sin x+…..\infty }}} $ , is

[MP PET 1998; Pb. CET 2001]

Options:

A) $ (2y-1)\frac{dy}{dx}-\sin x=0 $

B) $ (2y-1)\cos x+\frac{dy}{dx}=0 $

C) $ (2y-1)\cos x-\frac{dy}{dx}=0 $

D) $ (2y-1)\cos x+\frac{dy}{dx}=0 $

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Answer:

Correct Answer: D

Solution:

$ y=\sqrt{\sin x+\sqrt{\sin x+\sqrt{\sin x+…..\infty }}} $

$ \Rightarrow y=\sqrt{\sin x+y}\Rightarrow y^{2}=\sin x+y $

On differentiating both sides, we get $ 2y\frac{dy}{dx}=\cos x+\frac{dy}{dx}\Rightarrow \frac{dy}{dx}(2y-1)=\cos x $ .