How to create better dots in continued fraction

Consider

 $$\left( a_1, a_2, \cdots a_m \right) \mapsto a_1 + \frac{1}{a_2 + \frac{1}{\cdots + \frac{1}{a_m}}}$$


I want to change the cdots into three dots like the following

dot
space dot
space space dot

(Can't find the words to describe this in English.)

Question: Is there an easy way to do this?

• The word is probably 'diagonal'.
– N.N.
Aug 27, 2011 at 11:23
• What do you mean with "magnified of course"?
– N.N.
Aug 27, 2011 at 12:04
• Removed that to prevent Babylonian type of comms. ;-) Aug 27, 2011 at 13:41

1. Use \ddots for diagonal dots (see §3.12. "Punctuation" in Short Math Guide for LaTeX).

2. Also consider to use \cfrac for continued fractions (see §5.4. "Continued fractions" in Short Math Guide for LaTeX).

\documentclass{article}

\usepackage{amsmath}% For \cfrac in the second example

\begin{document}

$% Here I've just changed the second occurence of \cdots to \vdots \left( a_1, a_2, \cdots a_m \right) \mapsto a_1 + \frac{1}{a_2 + \frac{1}{\ddots \, + \frac{1}{a_m}}}$

$% \cfrac instead of \frac . This looks much better! \left( a_1, a_2, \cdots a_m \right) \mapsto a_1 + \cfrac{1}{a_2 + \cfrac{1}{\ddots \, + \cfrac{1}{a_m}}}$

\end{document}


\documentclass{article}
\usepackage{amsmath}

\begin{document}

$\left( a_1, a_2, \cdots a_m \right) \mapsto a_1 + \dfrac{1}{a_2 + \dfrac{1}{\mkern10mu\raisebox{-0.25\height}{\ddots} + \dfrac{1}{a_m}}}$

\end{document}


• \dfrac is the same as displaystyle\frac
• \mkern reserves space in math units (1mu=1/18 em)
• \raisebox is self explanatory