VIT Engineering VIT Engineering Solved Paper-2008

  • question_answer
    Argument of the complex number\[\left( \frac{-1-3i}{2+i} \right)\]is

    A)  \[45{}^\circ \]            

    B)  \[135{}^\circ \]

    C)  \[225{}^\circ \]          

    D)  \[240{}^\circ \]

    Correct Answer: C

    Solution :

    \[\left( \frac{-1-3\,i}{2+i} \right)=\frac{-1-3i}{2+i}\times \frac{2-i}{2-i}\] \[=\frac{-2+i-6i+3{{i}^{2}}}{4+1}\] \[=\frac{-2-5i-3}{5}=\frac{-5-5i}{5}=-1-i\] \[\therefore \]Argument of \[\left( \frac{-1-3i}{2+i} \right)={{\tan }^{-1}}\left( \frac{-1}{-1} \right)\]   \[=225{}^\circ \] [ Since the given number lies on a 3rd quadrant ]


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