J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    For \[0<\theta <\pi ,\] if  \[A=\left[ \begin{matrix}    \cos \theta  & -\sin \theta   \\    \sin \theta  & \cos \theta   \\ \end{matrix} \right],\]then

    A)  \[{{A}^{T}}=A\]        

    B)  \[{{A}^{T}}=-A\]

    C)  \[{{A}^{2}}=I\]

    D)  \[{{A}^{T}}={{A}^{-1}}\]

    Correct Answer: D

    Solution :

    Given, \[A=\left[ \begin{matrix}    \cos \,\theta  & -\sin \theta   \\    \sin \theta  & \cos \theta   \\ \end{matrix} \right]\] \[\therefore \]  \[{{A}^{-1}}\left[ \begin{matrix}    \cos \theta  & \sin \theta   \\    -\sin \theta  & \cos \theta   \\ \end{matrix} \right]={{A}^{T}}\]


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