Documentation 
Section: (Usage) 3.5.11.?To Use Functions
3. Click on the Value field, then enter the new value. Use the keyboard
shortcuts to invoke a Calculator button. For example, enter 90K to calculate
sine(90).

Correct version:
A couple of simple working examples. A Farenheit to Celcius conversion example
might be nice, if possible. Can the function use the number already on the
display or is it not really a function so it can only hold a constant?

Other information:
Even though I'm not using the most recent version, I didn't see a bug report in
bugzilla and I couldn't find the change in the changelog so I'm posting this
bug. The help file says you should be able to create a function, that takes the
sin of 90 degrees, by entering 90K in the value field of the Edit Functions
dialog box. It doesn't seem to work. Only simple expressions such as 2+3*4= 
gave results. It took a lot of trial and error to figure out how to get it to
give me anything but a malformed function error. While the function syntax
seems obvious in hindsight, I kept trying various things like standard
spreadsheet notation =2+3*4 and plain old 2+3*4  Is there any way to include
the display value so that the user functions are actually functions and not
just constant expressions? I'm running Ubuntu 6.06

(Originally filed as bug #348765).