ThmDex – An index of mathematical definitions, results, and conjectures.
Interchanging two rows or two columns of a real square matrix switches the sign of the determinant
Formulation 0
Let $A \in \mathbb{R}^{N \times N}$ be a D6160: Real square matrix such that
(i) $N \in \{ 2, 3, 4, \ldots \}$ is a D5094: Positive integer
(ii) $a_1, \ldots, a_N \in \mathbb{R}^{N \times 1}$ are each a D5200: Real column matrix
(iii) $b_1, \ldots, b_N \in \mathbb{R}^{1 \times N}$ are each a D5201: Real row matrix
(iv) \begin{equation} A = \begin{bmatrix} a_1 & a_2 & \cdots & a_N \end{bmatrix} \end{equation}
(v) \begin{equation} A = \begin{bmatrix} b_1 \\ b_2 \\ \vdots \\ b_N \end{bmatrix} \end{equation}
(vi) $\pi : \{ 1, \ldots, N \} \to \{ 1, \ldots, N \}$ is a D6177: Standard transposition
(vii) \begin{equation} X = \begin{bmatrix} a_{\pi(1)} & a_{\pi(2)} & \cdots & a_{\pi(N)} \end{bmatrix} \end{equation}
(viii) \begin{equation} Y = \begin{bmatrix} b_{\pi(1)} \\ b_{\pi(2)} \\ \vdots \\ b_{\pi(N)} \end{bmatrix} \end{equation}
Then
(1) \begin{equation} \text{Det} X = - \text{Det} A \end{equation}
(2) \begin{equation} \text{Det} Y = - \text{Det} A \end{equation}
Proofs
Proof 0
Let $A \in \mathbb{R}^{N \times N}$ be a D6160: Real square matrix such that
(i) $N \in \{ 2, 3, 4, \ldots \}$ is a D5094: Positive integer
(ii) $a_1, \ldots, a_N \in \mathbb{R}^{N \times 1}$ are each a D5200: Real column matrix
(iii) $b_1, \ldots, b_N \in \mathbb{R}^{1 \times N}$ are each a D5201: Real row matrix
(iv) \begin{equation} A = \begin{bmatrix} a_1 & a_2 & \cdots & a_N \end{bmatrix} \end{equation}
(v) \begin{equation} A = \begin{bmatrix} b_1 \\ b_2 \\ \vdots \\ b_N \end{bmatrix} \end{equation}
(vi) $\pi : \{ 1, \ldots, N \} \to \{ 1, \ldots, N \}$ is a D6177: Standard transposition
(vii) \begin{equation} X = \begin{bmatrix} a_{\pi(1)} & a_{\pi(2)} & \cdots & a_{\pi(N)} \end{bmatrix} \end{equation}
(viii) \begin{equation} Y = \begin{bmatrix} b_{\pi(1)} \\ b_{\pi(2)} \\ \vdots \\ b_{\pi(N)} \end{bmatrix} \end{equation}