CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    If\[\left| \frac{z-i}{z+i} \right|=1,\]then the locus of 2 is:

    A)  \[x=0\]               

    B)         \[y=0\]

    C)  \[x=1\]               

    D)         \[y=1\]

    E)  none of these

    Correct Answer: B

    Solution :

    \[\because \]\[\left| \frac{z-i}{z+i} \right|=1\] Let \[z=x+iy\] \[\therefore \]  \[\left| \frac{x+iy-i}{x+iy+i} \right|=1\] \[\Rightarrow \]               \[\left| \frac{x+i(y-1)}{x+i(y+1)} \right|=1\] \[\Rightarrow \]               \[{{x}^{2}}+{{(y-1)}^{2}}={{x}^{2}}+{{(y+1)}^{2}}\] \[\Rightarrow \]               \[-2y=2y\]\[\Rightarrow \]\[4y=0\] Thus, the locus of z is\[y=0\].


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