Math : acos()

public class Acos {

    public static void main(String[] args)
    {
        double degrees = 45.0;        double radians = Math.toRadians(degrees);
        System.out.format("The value of pi is %.4f%n", Math.PI);        System.out.format("The arccosine of %.4f is %.4f degrees %n", Math.cos(radians),        Math.toDegrees(Math.acos(Math.sin(radians))));    }
}