You can enter LaTeX expresions on the wiki.
The LaTeX is handled using ASCIIMathML:
http://moinmoin.wikiwikiweb.de/MathMlSupport
http://project.knowledgeforge.net/sciki/svn/
http://project.knowledgeforge.net/sciki/svn/trunk/INSTALL.txt
This allows you to insert text like:
$$c=sqrt{(a2+b2)/2}$$
$$x = y + z$$
$$\textrm{Supply} = \textrm{Demand} * c$$
Subscripts: $$x_{1} = y_{1} + z_{2}$$
You may need to configure your browser for this to show up correctly:
http://www.weizmann.ac.il/student-wiki/HelpOnMathML
Your browser will probably warn you that the MathML feature is not working and give you instructions what to do.