Pi Cubed version 1.01 now on the App Store
A calculation error involving subtraction operations had been reported, and that should now be fixed. Thanks go to warnerdan42 for pointing this out. The drag force equation was missing an exponent, and a couple of the equations were awkwardly formatted, so those have been improved.
This also adds a new editing capability: the ability to select and delete a surrounding mathematical operation without deleting its contents. For example, in a calculation like sin (3 + 5), you can now delete the sine operation, leaving behind (3 + 5). To do this, tap once to select the whole sine portion of the calculation, and a second time to select just the surrounding operation. When you tap the delete button, only the surrounding operation will be deleted.
This should make it much easier to enter and edit equations without having to redo your work if you tap the wrong menu item.