Answer
One example is $\begin{bmatrix}
1&0&0\\
0&2&0\\
0&0&3
\end{bmatrix}$
Work Step by Step
Diagonal matrix is a square matrix in which all its non diagonal elements are zero. There will be 3 rows and 3 columns in a 3×3 matrix. An example for a 3×3 diagonal matrix is $\begin{bmatrix}
1&0&0\\
0&2&0\\
0&0&3
\end{bmatrix}$.
