3 dots in matrix

Question

I was wondering if anyone knew how to draw 3 dots in a matrix that go in a diagonal way usually to represent that element flow similarily in the slots. I know there's one that goes in the bottom right corner. But is there one that goes in the bottom left?

Answer 1

The MnSymbol package provides \udots that prints 3 dots going from NE to SW; in the opposite direction of \ddots which goes from NW to SE.

Similar dots are provided by \iddots from mathdots and \adots from yhmath. See p 60 of the Comprehensive LaTeX symbol list. You could also use \reflectbox{<stuff>} from the graphicx package to reflect something about the vertical axis.

Here's a brief overview:

\documentclass{article}
\usepackage{graphicx}% http://ctan.org/pkg/graphicx
\usepackage{yhmath}% http://ctan.org/pkg/yhmath
\usepackage{mathdots}% http://ctan.org/pkg/mathdots
\usepackage{MnSymbol}% http://ctan.org/pkg/mnsymbol
\begin{document}
Different versions of diagonal dots:

$\renewcommand{\arraystretch}{1.5}%
  \begin{array}{ll}
    \verb!\ddots! & \ddots \\
    \verb!\udots! & \udots \\
    \verb!\iddots! & \iddots \\
    \verb!\adots! & \adots \\
    \verb!\reflectbox{$\ddots$}! & \reflectbox{$\ddots$}
  \end{array}
$
\end{document}

In addition to the above source of LaTeX symbols, Detexify is also a fast way to identify symbols in LaTeX. Remember to "Select from the complete list!" if you don't see your symbol immediately, since the scoring algorithm may be off, depending on the symbol (or one's drawing prowess).

Answer 2

For a good source to math symbols, I think the Comprehensive LaTeX symbol list is a complement to the very good document Mathmode.pdf. This document is interesting because it offers another organisation and you can find all about mathematics.