To get MathJax to work in Blogger, just go to your Blogger account, click "Design" (top right of the page), and then "Edit HTML". After the first

`<head>`

you see, paste<script src='http://cdn.mathjax.org/mathjax/latest/MathJax.js' type='text/javascript'> MathJax.Hub.Config({ HTML: ["input/TeX","output/HTML-CSS"], TeX: { extensions: ["AMSmath.js","AMSsymbols.js"], equationNumbers: { autoNumber: "AMS" } }, extensions: ["tex2jax.js"], jax: ["input/TeX","output/HTML-CSS"], tex2jax: { inlineMath: [ ['$','$'], ["\\(","\\)"] ], displayMath: [ ['$$','$$'], ["\\[","\\]"] ], processEscapes:true}, "HTML-CSS": { availableFonts: ["TeX"], linebreaks: { automatic:true} } }); </script>

You're done! You can now use the usual

`$...$`

or `\(...\)`

for inline equations, and `$$...$$`

or`\[...\]`

for equations that are centered in their own line.
Time for an example:

\[

\cos^2\theta-\sin^2\theta=\cos 2\theta.

\] The above script loads AMSmath and AMSsymbols so that the macros defined in these popular packages are available for use in your blog.

\begin{equation}\label{eq:gravt}

F=G\frac{mM}{r^2}.

\end{equation}Also,

\begin{equation}\label{eq:gravo}

F=mg,

\end{equation}and so equations (\ref{eq:gravt}) and (\ref{eq:gravo}) lead to\[

g=G\frac{M}{r^2},

\]assuming the equivalence of inertial and gravitational mass.

\[

\cos^2\theta-\sin^2\theta=\cos 2\theta.

\] The above script loads AMSmath and AMSsymbols so that the macros defined in these popular packages are available for use in your blog.

**UPDATE:**Equations can now be numbered and referred to. For example, in Newtonian gravity we have\begin{equation}\label{eq:gravt}

F=G\frac{mM}{r^2}.

\end{equation}Also,

\begin{equation}\label{eq:gravo}

F=mg,

\end{equation}and so equations (\ref{eq:gravt}) and (\ref{eq:gravo}) lead to\[

g=G\frac{M}{r^2},

\]assuming the equivalence of inertial and gravitational mass.