J & K CET Engineering J and K - CET Engineering Solved Paper-2012

  • question_answer
    The value of \[\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\sin \,(\pi \,co{{s}^{2}}x)}{{{x}^{2}}}\] is equal to

    A)  \[\frac{\pi }{2}\]               

    B)  \[\pi \]

    C)  \[-\pi \]

    D)  \[1\]

    Correct Answer: B

    Solution :

    \[\underset{x\to 0}{\mathop{\lim }}\,\,\frac{\sin \,(\pi \,{{\cos }^{2}}x)}{{{x}^{2}}}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\sin \,(\pi {{\cos }^{2}}x)}{{{x}^{2}}}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\sin \,(\pi \,{{\cos }^{2}}x)}{\pi \,{{\cos }^{2}}x}\times \frac{\pi \,{{\cos }^{2}}x}{{{x}^{2}}}\] \[=1\times \pi \times 1=\pi \] \[\left( \because \,\,\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\sin x}{x}=1\,and\,\,\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\cos \,x}{x}=1 \right)\]


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