JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    If \[f(x)=\sqrt{\frac{x-\sin x}{x+{{\cos }^{2}}x}}\], then \[\underset{x\to \infty }{\mathop{\lim }}\,f(x)\]is [DCE 2000]

    A)                 0

    B)                 \[\infty \]

    C)                 1

    D)                 None of these

    Correct Answer: C

    Solution :

                       \[\underset{x\to \infty }{\mathop{\lim }}\,\,\,f(x)=\,\underset{x\to \infty }{\mathop{\lim }}\,\,\sqrt{\frac{x-\sin x}{x+{{\cos }^{2}}x}}=\underset{x\to \infty }{\mathop{\lim }}\,\,\,\sqrt{\frac{1-\frac{\sin x}{x}}{1+\frac{{{\cos }^{2}}x}{x}}}\]                                 \[=\sqrt{\frac{1-0}{1+0}}=1\], \[\left( \because \,\,\,\frac{\sin x}{x}\to 0,\frac{{{\cos }^{2}}x}{x}\,\to 0\,\,\text{as }x\to \infty  \right)\].


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