JEE Main & Advanced AIEEE Paper (Held On 11 May 2011)

  • question_answer
    If \[\omega \ne 1\] is the complex cube root of unity and matrix \[H=\left[ \begin{matrix}    \omega  & 0  \\    0 & \omega   \\ \end{matrix} \right],\]then \[{{H}^{70}}\]is equal to -     AIEEE  Solved  Paper (Held On 11 May  2011)

    A)  \[0\]                    

    B) \[-H\]

    C) \[{{H}^{2}}\]

    D) \[H\]

    Correct Answer: D

    Solution :

                    \[{{H}^{2}}=\left[ \begin{matrix}    \omega  & 0  \\    0 & \omega   \\ \end{matrix} \right]\left[ \begin{matrix}    \omega  & 0  \\    0 & \omega   \\ \end{matrix} \right]=\left[ \begin{matrix}    {{\omega }^{2}} & 0  \\    0 & {{\omega }^{2}}  \\ \end{matrix} \right]\] If \[{{H}^{k}}=\left[ \begin{matrix}    \omega k & 0  \\    0 & \omega k  \\ \end{matrix} \right],\] So by mathematical induction, \[{{H}^{70}}=\left[ \begin{matrix}    {{\omega }^{70}} & 0  \\    0 & {{\omega }^{70}}  \\ \end{matrix} \right]=\left[ \begin{matrix}    \omega  & 0  \\    0 & \omega   \\ \end{matrix} \right]=H\]


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