CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2002

  • question_answer
    The function\[y=a(a-\cos x)\]is maximum when\[x\]is equal to:

    A)  \[\pi \]

    B)         \[\frac{\pi }{2}\]

    C)         \[-\frac{\pi }{2}\]                                            

    D)         \[-\frac{\pi }{6}\]

    E)         \[\frac{\pi }{3}\]

    Correct Answer: A

    Solution :

                                    \[\because \] \[y=a(1-\cos x)\] On differentiating w.r.t\[x,\]we get \[\frac{dy}{dx}=a\sin x\] Again differentiating w. r. t.\[x,\]we get                 \[\frac{{{d}^{2}}y}{d{{x}^{2}}}=a\cos x\] Put\[\frac{dy}{dx}=0\]for maxima or minima \[\Rightarrow \]               \[\sin x=0\Rightarrow x=\pi \] \[\therefore \]  \[{{\left( \frac{{{d}^{2}}u}{d{{x}^{2}}} \right)}_{x=\pi }}=a\cos \pi =-a\] \[\therefore \]Function is maximum at\[x=\pi \].


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