JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\tan 2x-x}{3x-\sin x}=\] [IIT 1971]

    A)                 0

    B)                 1

    C)                 ½

    D)                 1/3

    Correct Answer: C

    Solution :

                       \[\underset{x\to 0}{\mathop{\lim }}\,\,\,\,\frac{\tan \,\,2x-x}{3x-\sin x}=\underset{x\to 0}{\mathop{\lim }}\,\,\,\,\left\{ \frac{\frac{2\,\tan 2x}{2x}-1}{3-\frac{\sin x}{x}} \right\}=\frac{1}{2}.\]            Aliter : Apply L-Hospital?s rule                                 \[\underset{x\to 0}{\mathop{\lim }}\,\,\,\frac{\tan 2x-x}{3x-\sin x}=\underset{x\to 0}{\mathop{\lim }}\,\,\frac{2{{\sec }^{2}}2x-1}{3-\cos x}=\frac{2-1}{3-1}=\frac{1}{2}.\]


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