RAJASTHAN ­ PET Rajasthan PET Solved Paper-2006

  • question_answer
    If\[y=\sqrt{\sin x+\sqrt{\sin x+\sqrt{\sin x+.......,}}}\]then the value of\[\frac{dy}{dx}\]is

    A)  \[\frac{\cos x}{2y-1}\]

    B)  \[\frac{2y-1}{\cos x}\]

    C)  \[\frac{\cos y}{2x-1}\]

    D)  \[\frac{2x-1}{\cos y}\]

    Correct Answer: A

    Solution :

     Given, \[y=\sqrt{\sin x+\sqrt{\sin x+\sqrt{\sin x+......\infty }}}\] \[\Rightarrow \] \[y=\sqrt{\sin x+y}\] On squaring both sides, we get \[{{y}^{2}}=sin\,x+y\] On differentiating w.r.t.\[x,\]we get \[2y\frac{dy}{dx}=\cos x+\frac{dy}{dx}\] \[\Rightarrow \] \[\frac{dy}{dx}(2y-1)=\cos x\] \[\Rightarrow \] \[\frac{dy}{dx}=\frac{\cos x}{2y-1}\]


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