doc: dev: minor change.

doc/dev/documentation.org

@@ -90,7 +90,8 @@ https://orgmode.org/org.html#Emphasis-and-Monospace].
 If we export the file to PDF, org-mode use \LaTeX. So we can add some
 piece of \LaTeX into the document[fn:: See \LaTeX part in
 documentation: https://orgmode.org/org.html#Embedded-LaTeX]. For
-exemple, we can add math formula like =\[E=mc^2\]=:
+exemple, we can add math formula like =$E=mc^2$= ($E=mc^2$) or
+=\[E=mc^2\]=:
 
 \[E=mc^2\]