Formula Max provides access to a huge database of every mathematical or scientific formula one could imagine. The user interface is very clean and easy to use and makes it the simplest, easiest Formulas app available on the app store.
It holds over 1150 formulas covering all subjects: algebra, geometry, trigonometry, physics, chemistry, atomic physics! It's an app you can download in 9th grade and still find yourself using well into college and beyond. The formulas can be stored in a favorites section so you have easy access to the ones you are learning, studying, or using on a regular basis.
One of the coolest features is a full periodic table of the elements. Each element can be selected and the app will instantly display the atomic weight, position, and every other pertinent detail concerning that element. The app also gives definitions for each subject that it covers for easy reference and refreshing.
Compatible with iPhone, iPod touch, and iPad.