JEE Main & Advanced Mathematics Differentiation Question Bank Mock Test - Limits and Derivatives

  • question_answer
    If \[f(x)=0\]is a quadratic equation such that \[f(-\pi )=f(\pi )=0\]and \[f\left( \frac{\pi }{2} \right)=-\frac{3{{\pi }^{2}}}{4}\], then \[\underset{x\to -\pi }{\mathop{\lim }}\,\frac{f(x)}{\sin (sinx)}\]is equal to

    A) 0                                 

    B)  \[\pi \]

    C)  \[2\pi \]            

    D) none of these

    Correct Answer: C

    Solution :

    [c] Given \[f(x)={{x}^{2}}-{{\pi }^{2}}\] \[\underset{x\to -\pi }{\mathop{\lim }}\,\frac{{{x}^{2}}-{{\pi }^{2}}}{\sin (sinx)}=\underset{h\to 0}{\mathop{\lim }}\,\frac{{{(-\pi +h)}^{2}}-{{\pi }^{2}}}{\sin (sin(-\pi +h))}\] \[\underset{h\to 0}{\mathop{\lim }}\,\frac{-2h\pi +{{h}^{2}}}{-\sin (sin+h)}\] \[\underset{h\to 0}{\mathop{\lim }}\,\frac{h-2\pi }{\frac{-\sin (sinh)}{\sinh }\times \frac{\sinh }{h}}=2\pi \]


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