PointF, Convert.ToString, method

public double Angle(PointF Pt1, PointF Pt2)  //**********
{
 double result;
 // 각도 계산
 result = Math.Atan((Pt2.Y - Pt1.Y) / (Pt2.X - Pt1.X));
 return result;
}

//**************
private void button1_Click(object sender, System.EventArgs e)
{
 PointF P1 = new PointF(-2.3f,3.1f);
 PointF P2 = new PointF(0.3f,-1.7f);

 double aa, bb;

 aa = Angle(P1, P2);
 bb = aa / Units.P_Angle.Phi * 180.0f;
 MessageBox.Show(Convert.ToString(Convert.ToString(bb)));
}