From Poliplus Software:
The Award Winning Formulae 1 (F1) is a powerful and easy to use Computer Algebra System designed specially for the teaching and exploration of mathematics. F1 gives the user the ability to see intermediate steps of calculations as well as final answers. The step feature has tremendous pedagogical value that users will come to appreciate over and over again.
While there are several different numerical based calculator programs for PDAs, there is nothing really that comes close to the mathematical capabilites of F1. Transform your PDA into the next generation handheld Mathematics system designed to get answers and see steps. If you are a student, this is a must have application.