# Centralizing the dots in equations

Folks, forgive me for answering this question. I'm unable to centralize dots in equations though i believe that the script is right. Could you please advise on the following:

\begin{equation*}
\begin{cases}
r_1.......\\
r_2.......\\
\vdots\\
r_n........
\end{cases}
\end{equation*}

• It would have been better if you provided a complete MWE. It is also not so clear what your problem is: Are you talking about the dots ....? If so, the answer is to replace them with \cdots. Or do you mean the horizontal placement of \vdots? If so, using cases is the wrong approach. As I see no ampersands (&) here, I wonder if cases is really what you want. A proper MWE might help to clear this up. – Harald Hanche-Olsen Oct 20 '18 at 6:57

You can have this simple code with mathtools (which is an extension of amsmath, so needless to load the latter package):

\documentclass{article}
\usepackage{mathtools}

\begin{document}

\begin{dcases} \begin{aligned} r_1 & =\cdots \\ r_2 & = \cdots \\[-1.5ex] &\vdotswithin{ = } \\[-1ex] r_n & = \cdots \end{aligned} \end{dcases}

\end{document}


Explanation:

the dcacses environment is a variant of the standard cases defined by mathtools in which everything is in \displaystyle. \vdotswithin{symbol} produces a \vdot centred w.r.t. the alignment symbol.

• aligned uses \displaystyle by itself. – egreg Oct 20 '18 at 10:42
• @egreg: yes, but I wanted to explain what's dcases w.r..t. cases. One does not always use cases with aligned. – Bernard Oct 20 '18 at 11:40

You might use array to achieve correct alignment. And use \left\{ ... \right. instead of cases

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{equation*}
\left\{
\begin{array}{lcl}
r_1 & = &.....\\
r_2 & = &.....\\
&\vdots&\\
r_n & = & .....
\end{array}
\right.
\end{equation*}

\end{document}


• using array gives weird spacing around the = and sets the items in textsyle not displaystyle, it would be far better to use an amsmath` alignment environment. – David Carlisle Oct 20 '18 at 8:38