Angles as objects that know what units they are in, know how to do trigonometry without needing help with unit conversion, and are therefore much less error-prone in lengthy calculations.
In java.lang.(Strict)Math you have to keep track of whether an angle is in degrees or radians when you use trigonometrical functions; the present class knows what to do, so you can forget about it! This should reduce the potential for errors of the degrees/radians kind.
A continual refrain in Jean Meeus' excellent series of books on astronomical computation is the risk of errors due to the fact that angles are usually given in degrees but trigonometry requires radians.
Calculate values of the Gaussian curve.
Static methods to do common mathematical calculations.
Just a record to hold public values.
Convenience record for holding a pair of doubles indicating the low and high ends of a range.
Miscellaneous useful static methods.
For formatting output values as strings.
Various units used for angles, and their symbols.