JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Mock Test - Matrices

  • question_answer
      If  then \[A{{(\alpha ,\beta )}^{-1}}\]is equal to

    A)  \[A(-\alpha ,-\beta )\]     

    B)  \[A(-\alpha ,\beta )\]

    C)  \[A(\alpha ,-\beta )\]      

    D)  \[A(\alpha ,\beta )\]

    Correct Answer: A

    Solution :

    [a] we have, \[A{{(\alpha ,\beta )}^{-1}}=\frac{1}{{{e}^{\beta }}}\left[ \begin{matrix}    {{e}^{\beta }}\cos \alpha  & -{{e}^{\beta }}\sin \alpha  & 0  \\    {{e}^{\beta }}\sin \alpha  & {{e}^{\beta }}\cos \alpha  & 0  \\    0 & 0 & 1  \\ \end{matrix} \right]\] \[=A(-\alpha ,-\beta )\]


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