JEE Main & Advanced Mathematics Differentiation Question Bank Self Evaluation Test - Limits and Derivatives

  • question_answer
    If \[\underset{x\to 0}{\mathop{\lim }}\,{{(1+asinx)}^{\cos ecx}}=3.\]then a is

    A) ln 2

    B) ln 3

    C) ln 4

    D) \[{{e}^{3}}\]

    Correct Answer: B

    Solution :

    [b] Given \[3=\underset{x\to 0}{\mathop{\lim }}\,{{(1+a\,sin\,x)}^{\cos ec\,x}}[{{1}^{\infty }}form]\] Put \[\sin x=4\] \[\therefore \] when \[x\to 0,y\to 0\] \[\therefore \underset{x\to 0}{\mathop{Lim}}\,{{(1+asinx)}^{\cos ecx}}=\underset{y\to 0}{\mathop{Lim}}\,{{(1+ay)}^{1/y}}={{e}^{a}}\] \[\therefore {{e}^{a}}=3\Rightarrow a={{\log }_{e}}3=ln\,3.\]


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