CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    \[{{\tan }^{-1}}\frac{m}{n}-{{\tan }^{-1}}\frac{m-n}{m+n}\]is equal to

    A)  \[{{\tan }^{-1}}\frac{n}{m}\]                     

    B)  \[{{\tan }^{-1}}\frac{m+n}{m-n}\]

    C)  \[\frac{\pi }{4}\]             

    D)  \[{{\tan }^{-1}}\left( \frac{1}{2} \right)\]

    E)  \[\frac{\pi }{2}\]

    Correct Answer: C

    Solution :

    \[{{\tan }^{-1}}\frac{m}{n}-{{\tan }^{-1}}\frac{m-n}{m+n}\] \[={{\tan }^{-1}}\frac{m}{n}-{{\tan }^{-1}}\frac{\frac{m}{n}-1}{1+\frac{m}{n}}\] \[={{\tan }^{-1}}\frac{m}{n}-{{\tan }^{-1}}\frac{m}{n}+{{\tan }^{-1}}(1)\] \[={{\tan }^{-1}}\left( \tan \frac{\pi }{4} \right)=\frac{\pi }{4}\]  


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