CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    The locus of z such that \[\arg [(1-2i)z-2+5i]\]\[=\frac{\pi }{4}\]is a

    A)  line not passing through the origin

    B)  circle not passing through the origin

    C)  line passing through the origin

    D)  circle passing through the origin

    E)  circle with centre at the origin

    Correct Answer: A

    Solution :

    \[\arg [(1-2i)z-2+5i]=\frac{\pi }{4}\] \[\Rightarrow \]\[\arg [(1-2i)(x+iy)-2+5i]=\frac{\pi }{4}\] \[\Rightarrow \]\[\arg [(x+2y-2)+i(y-2x+5)]=\frac{\pi }{4}\] \[\Rightarrow \]               \[{{\tan }^{-1}}\left[ \frac{y-2x+5}{x+2y-2} \right]=\frac{\pi }{4}\] \[\Rightarrow \]               \[\frac{y-2x+5}{x+2y-2}=1\] \[\Rightarrow \]               \[3x+y-7=0\] Which represents a line not passing through the origin.


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