RAJASTHAN ­ PET Rajasthan PET Solved Paper-2002

  • question_answer
    The value of\[\underset{x\to 0}{\mathop{\lim }}\,\frac{\sqrt{\frac{1}{2}(1-\cos 2x)}}{x}\]is

    A)  1              

    B)  \[-1\]

    C)  0              

    D)  None of these

    Correct Answer: D

    Solution :

     \[\underset{x\to 0}{\mathop{\lim }}\,\frac{\sqrt{\frac{1}{2}(1-\cos 2x)}}{x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{\sqrt{\frac{1}{2}.2{{\sin }^{2}}x}}{x}\] \[=\underset{x\to 0}{\mathop{\lim }}\,\pm \frac{\sin x}{x}\] Taking \[(+)sign,\underset{x\to 0}{\mathop{\lim }}\,\frac{\sin x}{x}=1\] Taking \[(-)sign,\underset{x\to 0}{\mathop{\lim }}\,\frac{-\sin x}{x}=-1\] \[\because \] \[\underset{x\to 0}{\mathop{\lim }}\,\frac{-\sin x}{x}=-1\] \[\therefore \] \[\underset{x\to 0}{\mathop{\lim }}\,\]does not exist.


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