Align equations not displaying?

[tgt]

The \begin{align} \end{align} is not displaying anything. What have I done wrong?

 

[cristo]

The \begin{align} \end{align} is not displaying anything. What have I done wrong?

Erm.. not put anything between the two commands?...

Seriously, it's very difficult to troubleshoot something if you don't give any information about your problem! Have you got the amsmath package installed?