Android Giveaway of the Day - VKRPN Scientific Calculator

VKRPN implements most of the functionality of a standard scientific calculator. Rather than simulate an old-fashioned physical calculator in all their cryptic details, its main goal is to expose a clean and legible interface while providing direct access to the essential mathematical operations. There is also available a list of constants and unit conversion factors as well as a comprehensive calculation history.

The calculator employs the so-called reverse Polish notation, where the operator follows its operands. For example, evaluation of 5+7 is accomplished as 5 ↓ 7 +. In this scheme the parentheses are not needed at all. Hence, expressions such as (3+7)·(8−4) are easier to enter and evaluate.

The list of features:
✓ Reverse Polish notation
✓ Arithmetic operations, power and trigonometric functions and their inverses, hyperbolic functions and their inverses, percent calculations (such as 50+10%=55)
✓ User can arbitrarily and unambiguously convert between radians, degrees and degrees/minutes/seconds
✓ Tabbed list of math/physics constants and unit conversion factors
✓ Unlimited log of calculation history, user can return any value from the logbook
✓ Adjustable precision and other number formatting options
✓ Themes
✓ Supports portrait and landscape orientation, adapts to different screen sizes
✓ Graphical help screens/tutorials
✓ Haptic feedback

The app contains no advertisements or in-app purchases and doesn't require any permissions (only vibration for haptic feedback).