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Question: Answered & Verified by Expert
If $A=\left[\begin{array}{cc}\cos \theta & -\sin \theta \\ \sin \theta & \cos \theta\end{array}\right]$, then which of the following statements is not correct ?
MathematicsMatricesJEE Main
Options:
  • A $A$ is orthogonal matrix
  • B $A^{\prime}$ is orthogonal matrix
  • C Determinant $A=1$
  • D $A$ is not invertible
Solution:
2438 Upvotes Verified Answer
The correct answer is: $A$ is not invertible
$|A|=1 \neq 0$, therefore $A$ is invertible.
Thus (4) is not correct.

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