double atan(double d)

public class Test { 

   public static void main(String args[]) {
      double degrees = 45.0;
      double radians = Math.toRadians(degrees);

      System.out.format("The value of pi is very very very approximately %.4f%n", Math.PI);
      System.out.format("The arctangent of %.4f is %.4f degrees %n", Math.cos(radians), 
         Math.toDegrees(Math.atan(Math.sin(radians))));
   }
}

The value of pi is very very very approximately 3.1416
The arctangent of 0.7071 is 35.2644 degrees