>> "rasmus" == rasmus  <Rasmus> writes:

   > Uwe Brauer <oub@mat.ucm.es> writes:
   >> Look the following examples 
   >> 
>> \begin{displaymath}
>> Xs,δ:=Hs,δ× Hs,δ+1× Hs,δ+1×
>> Hs+1,δ+2
>> \end{displaymath}
   >> org-preview-latex-fragment does not work, change displaymath for
   >> equation, again org-preview-latex-fragment does not work, but 
   >> \[ \]
   >> does work, this is odd


   > 1. The example you posted contains utf8 symbols and you'd likely need
   >    unicodemath (the package) to display it.  For this you'd need
   >    xelatex or lualatex.  But probably you wrote it as plain LaTeX code
   >    in your document.

Hm it seems that the coding was changed when sending the formula, since
I wrote \delta in the original mail not δ.

In any case: *why* does \[ \] work, if it is question of a missing package? 

   > 2. displaymath is from amsmath.  This works on my system:
   >    #+BEGIN_SRC org
   >    #+LATEX_HEADER: \usepackage{amsmath}
   >    \begin{displaymath}
   >    x=1
   >    \end{displaymath}
   >    #+END_SRC

Really?

Here is a minimal example 
of a LaTeX file, which is not using amsmath, but the file is compiled as
it should be:


\documentclass{article}

\begin{document}
\begin{displaymath}
  \int dx
\end{displaymath}
\end{document}



I also extended the corresponding configuration in org.el



(defcustom org-format-latex-header "\\documentclass[12pt]{article}
\\usepackage[usenames]{color}
\\usepackage{amsmath}
\\usepackage{plain}
\\usepackage[mathscr]{eucal}


Uwe