CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2006

  • question_answer
    If z is a complex number such that \[\operatorname{Re}(z)=\operatorname{Im}(z),\]then:

    A) \[\operatorname{Re}({{z}^{2}})=0\]      

    B)        \[\operatorname{Im}({{z}^{2}})=0\]

    C)  \[\operatorname{Re}({{z}^{2}})=\operatorname{Im}({{z}^{2}})\]

    D)         \[\operatorname{Re}({{x}^{2}})=-\operatorname{Im}({{z}^{2}})\]

    E) \[{{z}^{2}}=0\]

    Correct Answer: A

    Solution :

    Let\[z=x+iy\Rightarrow zz=(x+iy)(x+iy)\] \[={{x}^{2}}-{{y}^{2}}+2ixy\] \[=0+2ixy\]         \[\because \]     \[\operatorname{Re}(z)=\operatorname{Im}(z)\] \[\Rightarrow \]               \[\operatorname{Re}({{z}^{2}})=0\]      


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