Dots

The continuation dots ... are known as an ellipsis. They occur frequently enough in mathematics for LaTeX to have four commands to typeset them with the right spacing. They are

1. \cdots for center height dots.
2. \ddots for diagonal dots, which occur in matrices.
3. \ldots for lower height dots.
4. \vdots for vertical dots.

$a_1,\ldots, a_n$

produces

$a_1,\ldots, a_n$

$$
\left(
\begin{array}{ccc}
a_{11}&\cdots&a_{1n}\\
\vdots&\ddots&\vdots\\
a_{m1}&\cdots&a_{mn}
\end{array}
\right)
$$

produces

$$\left( \begin{array}{ccc} a_{11}&\cdots&a_{1n}\\ \vdots&\ddots&\vdots\\ a_{m1}&\cdots&a_{mn} \end{array}\right)$$

Practice: Construct a document using at least two different forms of dots.