JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{x\to a}{\mathop{\lim }}\,\frac{\cos x-\cos a}{\cos x-\cot a}=\] [BIT Ranchi 1987]

    A)                 \[\frac{1}{2}{{\sin }^{3}}a\]

    B)                 \[\frac{1}{2}\text{cose}{{\text{c}}^{2}}a\]

    C)                 \[{{\sin }^{3}}a\]

    D)                 \[\text{cose}{{\text{c}}^{3}}a\]

    Correct Answer: C

    Solution :

                    \[\underset{x\to a}{\mathop{\lim }}\,\,\frac{\cos x-\cos a}{\cot x-\cot a}=\underset{x\to a}{\mathop{\lim }}\,\,\left( \frac{-\sin x}{-\cos e{{c}^{2}}x} \right)=\underset{x\to a}{\mathop{\lim }}\,{{\sin }^{3}}x={{\sin }^{3}}a\].


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