public double a_angle()
	{
		double theta = Math.abs(Math.atan(y/x));
		if(x < 0 && y > 0)
			theta = Math.PI - theta;
		else if(x < 0 && y < 0)
			theta = Math.PI + theta;
		else if(x > 0 && y < 0)
			theta = 2*Math.PI - theta;
		return theta;
	}