Elements of the diagonal matrix will be along the diagonal. All the other positions except the diagonal position of the matrix will be filled by zero.

```
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[ \begin{bmatrix}
a_{1} & & & \\
& a_{2} & & \\
& & \ddots & \\
& & & a_{3}
\end{bmatrix} \]
\end{document}
```

**Output :**

And diagonal matrix is only valid in the case of a square matrix.

## Use physics package for diagonal matrix

In Latex, there are various arguments within the physics package that allow you to easily represent the diagonal matrix in a variety of ways.

```
\documentclass{article}
\usepackage{physics}
\begin{document}
\[ \mqty[ a_{1} & 0 & 0\\ 0 & a_{2} & 0\\ 0 & 0 & a_{3} ] \]
\end{document}
```

**Output :**

Second, you can use the `\dmat`

command. However, this `\dmat`

command must be passed as an argument in the `\mqty`

command without using direct.

```
\documentclass{article}
\usepackage{physics}
\begin{document}
\[ \mqty[\dmat{1,2,3,4}] \]
\end{document}
```

**Output :**

And with that, the elements of the diagonal matrix have to be passed into `\dmat`

command.

To fill in any position other than the diagonal position of the matrix by zero, you need to pass zero in the optional argument with `\dmat`

command.

```
\documentclass{article}
\usepackage{physics}
\begin{document}
\[ \mqty[\dmat[0]{1,2,3,4}] \]
\end{document}
```

**Output :**

## Inverse diagonal matrix in LaTeX

If you want to arrange the elements of the matrix along the inverse diagonal you need to use `\admat`

command instead of `\dmat`

command.

```
\documentclass{article}
\usepackage{physics}
\begin{document}
\[ \mqty[\admat{1,2,3,4}] \]
\[ \mqty[\admat[0]{1,2,3,4}] \]
\end{document}
```

**Output :**