JEE Main & Advanced Mathematics Limits, Continuity and Differentiability Question Bank Self Evaluation Test - Continuity and Differentiability

  • question_answer
    If \[f(x)={{(x+1)}^{\cot \,x}}\] is continuous at\[x=0\], then what is f (0) equal to?

    A) 1

    B) e

    C) \[\frac{1}{e}\]

    D) \[{{e}^{2}}\]

    Correct Answer: B

    Solution :

    [b] For a function to be continuous at a point the limit should exist and should be equal to the value of the function at that point. Here point is x = 0 and \[\underset{x\to 0}{\mathop{\lim }}\,f(x)=\underset{x\to 0}{\mathop{\lim }}\,{{(x+1)}^{\cot x}}\] \[=\underset{x\to 0}{\mathop{\lim }}\,{{(x+1)}^{\cot x}}=\underset{x\to 0}{\mathop{\lim }}\,{{(1+x)}^{\frac{1}{x}.x\cot x}}\] \[=\underset{x\to 0}{\mathop{\lim }}\,{{(x+1)}^{\frac{1}{x}\underset{x\to 0}{\mathop{\lim }}\,\frac{x}{\tan \,x}}}={{e}^{1}}=e\] Since limiting value of \[f(x)=e\], when \[x\to 0,f(0)\] should also be equal to e.


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