If \(A\) is a Skew-symmetric matrix then (given \(n \in \mathbf{N}\)) 1. \(A^{2 n}\) is Skew-symmetric…

If \(A\) is a Skew-symmetric matrix then (given \(n \in \mathbf{N}\)) 1. \(A^{2 n}\) is Skew-symmetric matrix. 2. \(A^{2 n+1}\) is Skew-symmetric matrix.
  1. 1 is true, 2 is false
  2. Both 1 and 2 are true
  3. Both 1 and 2 are false
  4. 1 is false, 2 is true

Solution

Given, \(A\) is a skew symmetric matrix \(\begin{aligned} \therefore \quad A^T & =-A \Rightarrow\left(A^{2 n}\right)^T=\left(A^T\right)^{2 n}=(-A)^{2 n} \\ \left(A^{2 n}\right)^T & =A^{2 n} \end{aligned}\) \(\therefore A^{2 n}\) is Symmetric Matrix \(\begin{aligned} & \left(A^{2 n+1}\right)^T=\left(A^T\right)^{2 n+1}=(-A)^{2 n+1} \\ & \left(A^{2 n+1}\right)^T=-A^{2 n+1} \end{aligned}\) \(A^{2 n+1}\) is skew symmetric Hence, option (d) is correct.

Asked in: AP EAMCET 2020 (18 Sep Shift 2)

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