JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2008

  • question_answer
        If\[\sec \theta =m\]and\[\tan \theta =n,\]then \[\frac{1}{m}\left[ (m+n)+\frac{1}{(m+n)} \right]\]is

    A)  \[2\]                                    

    B)  \[2m\]

    C)  \[2n\]                                  

    D)  \[mn\]

    Correct Answer: A

    Solution :

                    Given that,\[sec\theta =m\]and\[\tan \theta =n\] \[\therefore \]  \[\frac{1}{m}\left[ (m+n)+\frac{1}{(m+n)} \right]\] \[=\frac{1}{\sec \theta }\left[ \sec \theta +\tan \theta +\frac{1}{\sec \theta +\tan \theta } \right]\] \[=\frac{[{{\sec }^{2}}\theta +{{\tan }^{2}}\theta +2\sec \theta \tan \theta +1]}{\sec \theta (\sec \theta +\tan \theta )}\] \[=\frac{2\sec \theta +2\sec \theta \tan \theta }{\sec \theta (\sec \theta +\tan \theta )}\] \[=\frac{2\sec \theta (\sec \theta +\tan \theta )}{\sec \theta (\sec \theta +\tan \theta )}\] \[=2\]


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