Let the given matrix be \(A\).

\[ A = \begin{bmatrix} -1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix} \]

To find the inverse of \(A\), we need to find a matrix \(A^{-1}\) such that \(A \cdot A^{-1} = I\), where \(I\) is the identity matrix.

In this case, we can observe that if we multiply \(A\) by itself, we get the identity matrix:

\[ A \cdot A = \begin{bmatrix} -1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix} \begin{bmatrix} -1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix} = \begin{bmatrix} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{bmatrix} = I \]

Since \(A \cdot A = I\), it means that \(A^{-1} = A\).