JEE Main & Advanced Mathematics Functions Question Bank Continuity

  • question_answer
    In order that the function \[f(x)={{(x+1)}^{\cot \,x}}\] is continuous at \[x=0\], \[f(0)\] must be defined as [UPSEAT 2000; Kurukshetra CEE 2001; Pb. CET 2004]

    A)            \[f(0)=\frac{1}{e}\]

    B)            \[f(0)=0\]           

    C)            \[f(0)=e\]

    D)            None of these

    Correct Answer: C

    Solution :

               For continuity at \[x=0\], we must have \[f(0)=\underset{x\to 0}{\mathop{\text{lim}}}\,f(x)\]\[\underset{x\to \alpha }{\mathop{\lim }}\,\,\frac{1-\cos \,(a{{x}^{2}}+bx+c)}{{{(x-\alpha )}^{2}}}\]\[=\underset{x\to 0}{\mathop{\text{lim}}}\,{{\left\{ {{(1+x)}^{\frac{1}{x}}} \right\}}^{x\cot x}}\]                  \[=\underset{x\to 0}{\mathop{\text{lim}}}\,{{\left\{ {{(1+x)}^{\frac{1}{x}}} \right\}}^{\underset{x\to 0}{\mathop{\text{lim}}}\,\,\left( \frac{x}{\tan x} \right)}}\] \[={{e}^{1}}=e\].


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