It would be great to have a math editor in Notebook. However, since there is none for the time being, some ideas:
1. Use Microsoft Word's equation editor and copy that to Notebook
2. Download and use many of the free math editors that are available on the web. Do a Google search for "free math editor software"
3. Here is a free online math editor at http://www.homeschoolmath.net/worksheets/equation_editor.php
4. Katie Morrow created a Smartboard Notebook file with many math functions that you could copy and paste to make your Smartboard Notebooks. Download the file at http://www.box.net/encoded/16623320/174463490/56bd9d0f6aa5c3187355cb49a0e4e12d