MCQ
If $\mathrm{A}=\left[\begin{array}{ll}\cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha\end{array}\right]$ then $\mathrm{A}^{-1}=\ldots$
  • A
    $\left[\begin{array}{rr}1 / \cos \alpha & -1 / \sin \alpha \\ 1 / \sin \alpha & 1 / \cos \alpha\end{array}\right]$
  • $\left[\begin{array}{rr}\cos \alpha & -\sin \alpha \\ -\sin \alpha & \cos \alpha\end{array}\right]$
  • C
    $\left[\begin{array}{ll}-\cos \alpha & \sin \alpha \\ -\sin \alpha & \cos \alpha\end{array}\right]$
  • D
    $\left[\begin{array}{rr}-\cos \alpha & \sin \alpha \\ \sin \alpha & -\cos \alpha\end{array}\right]$

Answer

Correct option: B.
$\left[\begin{array}{rr}\cos \alpha & -\sin \alpha \\ -\sin \alpha & \cos \alpha\end{array}\right]$
$\left[\begin{array}{rr}\cos \alpha & -\sin \alpha \\ -\sin \alpha & \cos \alpha\end{array}\right]$

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