How to use RPN mode with Functions?

[Han]

In RPN entry, you need to place the argument(s) onto the stack. Then you would execute a command using COMMAND(n) where n is the number of arguments used by COMMAND. In this case, your command is F1. In algebraic notation, you would enter F1(5) to get 25. In RPN notation, you would place 5 onto the stack, and type F1(1).