public static int nizovi(double[]a , double[]b , double alfa)
{
    int BrStr = 0;
    for (int i = 0; i < b.length; i++)
    {
        double P12,P13, P23;
        P12 = duzina(a[i+1], b[i+1], a[i], b[i]);
        P13 = duzina(a[i+1], b[i+1], a[i+2], b[i+2]); // pisemo prvo i+1 jer je to vertex tacka, ona koja je u centru ugla, zato nije od i
        P23 = duzina(a[i], b[i], a[i+2], b[i+2]);

        double x = ugao(P12, P13, P23);
        if(x > alfa)
        {
            System.out.print( "Stranica : " + "( " + a[i] + "," + b[i] + " )" + "( " + a[i+1] + "," + b[i+1] + " )" + " & ");
            System.out.println("( " + a[i+1] + "," + b[i+1] + " )" + "( " + a[i+2] + "," + b[i+2] + " )");
            System.out.println();
            BrStr++;
        }


    }
    return BrStr;

}


public static double ugao (double P12, double P13, double P23)
{
    return Math.acos((Math.pow(P12, 2) + Math.pow(P13, 2) - Math.pow(P23, 2))/(2 * P12 * P13));
}


public static double duzina (double vertexX1, double vertexY1, double x2, double y2)
{
    return  Math.sqrt(Math.pow((vertexX1-x2),2)+ Math.pow((vertexY1-y2), 2));
}
public static void main(String[] args) {
    // TODO Auto-generated method stub

    double a[] = {12,25,3};
    double b[] = {11,20,5};

    nizovi(a, b, 45);

}