The original question was how to use avant font in the equations. The problem is solved:
I a Linux Debian Sarge I do: 1) Download "sansmath.sty" from: http://www.ctan.org/tex-archive/macros/latex/contrib/misc/ 2) With then command "kpsepath tex" you get the paths, where TeX search for files. I get: /home/totxo/texmf/tex/generic/ /usr/local/share/texmf/tex/generic/ /usr/local/lib/texmf/tex/generic/ /var/lib/texmf/tex/generic/ /usr/share/texmf/tex/generic/ /home/totxo/texmf/tex/ /usr/local/share/texmf/tex/ /usr/local/lib/texmf/tex/ /var/lib/texmf/tex/ /usr/share/texmf/tex/ 3) As root, make the directory -p /usr/local/share/texmf/tex/latex # mkdir -p /usr/local/share/texmf/tex/latex 4) As root, copy "sansmath.sty" to /usr/local/share/texmf/tex/latex/: # cp sansmath.sty /usr/local/share/texmf/tex/latex/ 3) Submit the command: # texhash 4) Start lyx 8) Put in the preamble (Format -> Document -> Preamble): \usepackage{sansmath} \sansmath and add commands like: \mathversion{sans} and \mathversion{normal} where necessary in your document. Tanks to William F. Adams, Herbert Voss and Roberto Marabini (http://www.mail-archive.com/lyx-users%40lists.lyx.org/msg11937.html)
