JEE Main & Advanced AIEEE Solved Paper-2002

  • question_answer
    If \[(\omega \ne 1)\] is a cubic root of unity, then \[\left| \begin{matrix}    1 & 1+i+{{\omega }^{2}} & {{\omega }^{2}}  \\    1-i & -1 & {{\omega }^{2}}-1  \\    -i & -1+\omega -i & -1  \\ \end{matrix} \right|\] equals   AIEEE  Solved  Paper-2002

    A) 0                

    B)           1                                

    C)           \[i\]                          

    D)           \[\omega \]

    Correct Answer: A

    Solution :

       Let \[\Delta =\left| \begin{matrix}    1 & 1+i+{{\omega }^{2}} & {{\omega }^{2}}  \\    1-i & -1 & {{\omega }^{2}}-1  \\    -i & -1+\omega -i & -1  \\ \end{matrix} \right|\]. Applying \[({{R}_{1}}\to {{R}_{1}}+{{R}_{3}})\] \[=\left| \begin{matrix}    1-i & -1 & {{\omega }^{2}}-1  \\    1-i & -1 & {{\omega }^{2}}-1  \\    -i & -1+\omega -i & -1  \\ \end{matrix} \right|=0\] (\[\because \] two rows are identical \[\therefore \omega +{{\omega }^{2}}=1\])


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