Formulus HD - Formulas for Calculus:
FormulasHD is the perfect study tool. It is a simple, easy to use, easy to navigate collection of the most important formulas and topics for high school and college students taking Calculus and Differential Equations.
All formulas are HI-RES, meaning you can pinch & zoom in to see that one formula you need up close! That also means that the app file size is very large, so you can't download FormulusHD over 3G!
I recommend this app for all math classrooms. It will both inform and engage the students.