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

  • question_answer
    If A is a square matrix, then \[A{{A}^{T}}\] is a

    A) Skew-symmetric matrix

    B) Symmetric matrix

    C) Diagonal matrix

    D) None of these

    Correct Answer: B

    Solution :

    [b] Let \[A=\left[ \begin{matrix}    1 & -1 & 1  \\    2 & 1 & 0  \\    1 & -1 & 2  \\ \end{matrix} \right],\] then \[A'=\left[ \begin{matrix}    1 & 2 & 1  \\    -1 & 1 & -1  \\    1 & 0 & 2  \\ \end{matrix} \right]\] \[\therefore AA'=\left[ \begin{matrix}    1 & -1 & 1  \\    2 & 1 & 0  \\    1 & -1 & 2  \\ \end{matrix} \right]\left[ \begin{matrix}    1 & 2 & 1  \\    -1 & 1 & -1  \\    1 & 0 & 2  \\ \end{matrix} \right]=\left[ \begin{matrix}    3 & 1 & 4  \\    1 & 5 & 1  \\    4 & 1 & 4  \\ \end{matrix} \right]\]


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