JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to \infty }{\mathop{\lim }}\,\frac{\sin x}{x}=\] [IIT 1975; MP PET 2004]

    A)                 1

    B)                 0

    C)                 Does not exist

    D)                 None of these

    Correct Answer: B

    Solution :

                       \[\underset{x\to \infty }{\mathop{\lim }}\,\,\,\frac{\sin x}{x},\] let \[x=\frac{1}{y}\] or \[y=\frac{1}{x},\] so that \[x\to \infty \,\,\Rightarrow \,y\to 0\]                 \[\therefore \,\underset{x\to \infty }{\mathop{\lim }}\,\,\left( \frac{\sin x}{x} \right)=\underset{y\to 0}{\mathop{\lim }}\,\,\left( y.\sin \frac{1}{y} \right)=\underset{y\to 0}{\mathop{\lim }}\,\,y\times \underset{y\to 0}{\mathop{\lim }}\,\,\sin \frac{1}{y}=0\times ...=0\]


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