Calculating PI with the law of Cosines (Wont Work)

package picomputer;

im****t static java.lang.Math.*;
im****t java.util.*;


public class Main
{
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);


        System.out.print("Enter angel A: ");
        double A = in.nextDouble();
        System.out.print("Enter circle radius: ");
        double radius = in.nextDouble();


        double a = pow(radius, A) * 2;
        a -= (2 * radius * radius) * cos(a);
        a = sqrt(a);


        double circ = a * (360 / A);


        System.out.println(circ * (radius / 2));
    }