NeoCal for Pocket PC User Guide
The angular mode buttons (, , and ) specify whether angles are measured in degrees, radians, or grads. The RAD and GRAD indicators are displayed to indicate those modes, while the absence of these indicators implies degrees mode.
The following functions modify the number in the x register:
Pressing before any of the above functions accesses the hyperbolic functions. The button recalls the value of pi into the x register.