Matrices

Concept:A diagonal matrix has all non‑diagonal entries equal to zero.Explanation:The given matrix is $\begin{bmatrix} 1 & 0 & 0 \\ 0 & -2 & 0 \\ 0 & 0 & 0 \end{bmatrix}$.All elements outside the main diagonal are zero, so it is a diagonal matrix.It is not an identity matrix because the diagonal entries are not all $1$.It is not skew symmetric because for a skew symmetric matrix $A^T = -A$, which would require all diagonal entries to be zero (here they are $1$ and $-2$).It is a square matrix, but “diagonal matrix” is the more specific and correct classification.Answer:Diagonal matrix