JEE Main & Advanced Mathematics Functions Question Bank Continuity

  • question_answer
    If \[f(x)\,=\frac{2-\sqrt{x+4}}{\sin 2x},\,\,(x\ne 0),\] is continuous function at \[x=0\], then \[f(0)\] equals    [MP PET 2002]

    A)            \[\frac{1}{4}\]

    B)            \[-\frac{1}{4}\]

    C)            \[\frac{1}{8}\]

    D)            \[-\frac{1}{8}\]

    Correct Answer: D

    Solution :

               If \[f(x)\] is continuous at \[x=0,\] then            \[f(0)\,=\,\underset{x\to 0}{\mathop{\lim }}\,f(x)\] \[=\underset{x\to 0}{\mathop{\lim }}\,\frac{2-\sqrt{x+4}}{\sin 2x}\],     \[\left( \frac{0}{0}\text{ }\,\text{form} \right)\]            Using L?Hospital?s rule, \[f(0)=\underset{x\to 0}{\mathop{\lim }}\,\frac{\left( -\frac{1}{2\sqrt{x+4}} \right)}{2\cos 2x}=-\frac{1}{8}\].


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