CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    The argument of the complex number\[\left( \frac{i}{2}-\frac{2}{i} \right)\]is equal to

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

    B)                         \[\frac{3\pi }{4}\]

    C)  \[\frac{\pi }{12}\]                           

    D)         \[\frac{\pi }{2}\]

    E)  \[\frac{3\pi }{2}\]

    Correct Answer: D

    Solution :

    Let \[z=\frac{i}{2}-\frac{2}{i}=\frac{i}{2}-\frac{2i}{{{i}^{2}}}\] \[Z=\frac{i}{2}+2i=\frac{5}{2}i=0+\frac{5}{2}i\] \[\arg (z)={{\tan }^{-1}}\left( \frac{\operatorname{Im}(z)}{\operatorname{Re}(z)} \right)\] \[={{\tan }^{-1}}\left( \frac{5/2}{0} \right)={{\tan }^{-1}}(\infty )\] \[={{\tan }^{-1}}\left( \tan \frac{\pi }{2} \right)=\frac{\pi }{2}\]


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