Here is some of the documentation (find this on the Web with a search for "Java cos"):
java.lang Class Math ... cos public static double cos(double a) Returns the trigonometric cosine of an angle.
cos is a static function of the class
which is found in the
Classes from that package (such as
are so common that you do not have to import the package.
a is a
double and must be expressed in radians.
The return value is a
(Math Review: ) Can angles in radian mesure be converted to degrees?