JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2012

  • question_answer
        If\[\tan (A+B)=p,\tan (A-B)=q,\]then the value of tan 2A is

    A)  \[\frac{p+q}{p-q}\]                       

    B)  \[\frac{p-q}{1+pq}\]

    C)  \[\frac{1+pq}{1-p}\]                     

    D)  \[\frac{p+q}{1-pq}\]

    Correct Answer: D

    Solution :

                    Let \[A=\underset{x\to \infty }{\mathop{\lim }}\,{{x}^{1/x}}\] Taking log on both sides, we get \[\log A=\underset{x\to \infty }{\mathop{\lim }}\,\frac{1}{x}\log x\]       \[\Rightarrow \]               \[\log A=0\]                                 \[\left( \because \underset{x\to \infty }{\mathop{\lim }}\,\frac{\log x}{{{x}^{m}}}=0\,\,\forall m>0 \right)\] \[\Rightarrow \]               \[A={{e}^{0}}=1\] \[\Rightarrow \]               \[\underset{x\to \infty }{\mathop{\lim }}\,{{x}^{1/x}}=1\]


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