BCECE Engineering BCECE Engineering Solved Paper-2009

  • question_answer
    The value of \[4+5{{\left( -\frac{1}{2}+\frac{i\sqrt{3}}{2} \right)}^{334}}+3{{\left( -\frac{1}{2}+\frac{i\sqrt{3}}{2} \right)}^{365}}\]is

    A) \[1-i\sqrt{3}\]   

    B)         \[-1+i\sqrt{3}\]

    C)         \[i\sqrt{3}\]                      

    D)         \[-i\sqrt{3}\]

    Correct Answer: C

    Solution :

    \[4+5{{\left( -\frac{1}{2}+\frac{i\sqrt{3}}{2} \right)}^{334}}+3{{\left( -\frac{1}{2}+\frac{i\sqrt{3}}{2} \right)}^{365}}\] \[=4+5{{(\omega )}^{334}}+3{{(\omega )}^{365}}\] \[=4+5{{(\omega )}^{333}}\omega +3{{(\omega )}^{363}}{{\omega }^{2}}\] \[=4+5\omega +3{{\omega }^{2}}\] \[=4+3(\omega +{{\omega }^{2}})+2\omega \] \[=4+3(-1)+2\left( \frac{-1+i\sqrt{3}}{2} \right)\] \[=1-1+i\sqrt{3}\] \[=i\sqrt{3}\]


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