CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2004

  • question_answer
    The locus of point z satisfying\[\operatorname{Re}\left( \frac{1}{z} \right)=k,\] where k is a non- zero real number, is:

    A)  a straight line  

    B)  a circle

    C)  an ellipse       

    D)         a hyperbola

    E)  none of these

    Correct Answer: B

    Solution :

     Let\[z=x+iy,\]then \[\operatorname{Re}\left( \frac{1}{z} \right)=k\] \[\Rightarrow \]               \[\operatorname{Re}\left( \frac{1}{x+iy} \right)=k\] \[\Rightarrow \]\[\operatorname{Re}\left( \frac{x}{{{x}^{2}}+{{y}^{2}}}-\frac{iy}{{{x}^{2}}+{{y}^{2}}} \right)=k\] \[\Rightarrow \]               \[k=\frac{x}{{{x}^{2}}+{{y}^{2}}}\] \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-\frac{1}{k}x=0\] which is an equation of circle.


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