The Calculator allows you to enter your own set of constants and to define your own functions through the Con and Fun keys shown in Figure 8-10.
Each of these keys has a menu associated with it, which you display by pressing MENU on the key. Choosing the first item from the menu displays a window that lets you enter the value of a constant or a function, and associate a name with that value. The numbers you enter are stored in a .calctoolrc file in your home directory.
Once you have entered the new value, the new value and its name are displayed in the pop-up menu associated with that Calculator key. To use the constant or function value, choose the desired item from the pop-up menu.