With JaTeX you can place mathematical function and all other TeX related features on your website with in your texts.
A small demo you can see at: http://demo.schultschik.com/jatex
For JaTeX the LaTeX Code have to be between {jatex}LATEXCODE{/jatex}. Since v1.4.0 $...$ works as well.
You have trouble using the extension? Write an issue at github or see the support website which other possibilities you have.