JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Self Evaluation Test - Matrices

  • question_answer
    If \[A=\left[ \begin{matrix}    0 & -1  \\    1 & 0  \\ \end{matrix} \right]\], then \[{{A}^{16}}\] is equal to:

    A) \[\left[ \begin{matrix}    0 & -1  \\    1 & 0  \\ \end{matrix} \right]\]

    B) \[\left[ \begin{matrix}    0 & 1  \\    1 & 0  \\ \end{matrix} \right]\]

    C) \[\left[ \begin{matrix}    -1 & 0  \\    0 & 1  \\ \end{matrix} \right]\]

    D) \[\left[ \begin{matrix}    1 & 0  \\    0 & 1  \\ \end{matrix} \right]\]

    Correct Answer: D

    Solution :

    [d] We have \[A=\left[ \begin{matrix}    0 & -1  \\    1 & 0  \\ \end{matrix} \right]\] Now, \[{{A}^{2}}=A.A=\left( \begin{matrix}    0 & -1  \\    1 & 0  \\ \end{matrix} \right)\left( \begin{matrix}    0 & -1  \\    1 & 0  \\ \end{matrix} \right)=\left( \begin{matrix}    -1 & 0  \\    0 & -1  \\ \end{matrix} \right)=-I\] where \[I=\left( \begin{matrix}    1 & 0  \\    0 & 1  \\ \end{matrix} \right)\] is identity matrix \[{{({{A}^{2}})}^{8}}={{(-I)}^{8}}=I\]. Hence, \[{{A}^{16}}=I\]


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