Ivor Horton's Beginning Java™ 2, JDK™ 5th Edition

2.8. Mathematical Functions and Constants

Sooner or later you are likely to need mathematical functions in your programs, even if it's only to obtain an absolute value or calculate a square root. Java provides a range of methods that support such functions as part of the standard library that is stored in the package java.lang, and all these are available in your program automatically.

The methods that support various additional mathematical functions are implemented in the Math class as static methods, so to reference a particular function you can just write Math and the name of the method you wish to use separated by a period. For example, the sqrt() method calculates the square root of whatever you place between the parentheses. To use the sqrt() method to produce the square root of the floating-point value that you've stored in a variable, aNumber, you would write Math.sqrt(aNumber).

The class Math includes a range of methods for standard trigonometric functions:

Method	Function	Argument Type	Result Type
sin(arg)	sine of the argument	double in radians	double
cos(arg)	cosine of the argument	double in radians	double
tan(arg)	tangent of the argument	double in radians	double
asin(arg)	sin−1 (arc sine) of the argument	double	double in radians, with values from −π/2 to π/2.
acos(arg)	cos−1 (arc cosine) of the argument	double	double in radians, with values from 0.0 to π.
atan(arg)	tan−1 (arc tangent) of the argument	double	double in radians, with values from −π/2 to π/2.
atan2 (arg1,arg2)	tan−1 (arc tangent) ...