An arithmetic formula of one argument ‘x’ may be entered using the F(x) SQL element. This element will result in the appropriate SQL for the formula being generated after replacing the argument ‘x’ in the formula with the SQL for the argument in the tree.
Variable Creation > Input > Variables: SQL Elements pane - Other > F(x)
A Column or other expression can be moved into the (empty) branch of the tree representing the argument ‘x’. The formula to generate SQL for is specified in the Properties panel. Double-click on F(x) or highlight it and click Properties to create or edit the desired formula.