JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Self Evaluation Test - Complex Numbers and Quadratic Equations

  • question_answer
    Let \[z={{\log }_{2}}(1+i),\] then \[(z+\bar{z})+i(z-\bar{z})=\]

    A) \[\frac{\ln \,4+\pi }{\ln \,\,4}\]       

    B) \[\frac{\pi -\ln \,4}{\ln \,\,2}\]

    C) \[\frac{\ln \,4-\pi }{\ln \,\,4}\]

    D) \[\frac{\pi +\ln \,\,4}{\ln \,\,2}\]

    Correct Answer: C

    Solution :

    \[\operatorname{z}=lo{{g}_{2}}\left( 1+i \right)=lo{{g}_{2}}\left( \sqrt{2}{{e}^{i\pi /4}} \right)\] \[=\,\,\,\frac{1}{2}+i\frac{\pi }{4}{{\log }_{2}}e\] \[\therefore \,\,\,z+\bar{z}=1\,\,and\,\,z-\bar{z}=i\frac{\pi }{2}{{\log }_{2}}e\] Hence, \[\left( z+\bar{z} \right)+i\left( z\,-\bar{z} \right)\] \[=\,\,1-\frac{\pi }{2}{{\log }_{2}}e=1-\frac{\pi }{2\,\,\ln 2}=\frac{\ln \,\,4-\pi }{\ln \,\,4}\]


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