[C #] quickly finding the angle between three points

Public static double Angle (Point cen, Point first, Point second)
{
Const double m_pi= 3.1415926535897;

Double ma_x = first. X-cen. X;
Double ma_y = first. Y-cen. Y;
Double mb_x = second. X-cen. X;
Double mb_y = second. Y-cen. Y;
Double v1 = (ma_x * mb_x) + (ma_y * mb_y );
Double ma_val = Math. Sqrt (ma_x * ma_x + ma_y * ma_y );
Double mb_val = Math. Sqrt (mb_x * mb_x + mb_y * mb_y );
Double cosM = v1/(ma_val * mb_val );
Double angleAMB = Math. Acos (cosM) * 180/M_PI;

Return angleAMB;
}

Private void button#click (object sender, RoutedEventArgs e)
{
System. Windows. Point button2Point = new System. Windows. Point (0, 0 );
System. Windows. Point button3Point = new System. Windows. Point (0, 5 );
System. Windows. Point button4Point = new System. Windows. Point (2, 5 );
System. Windows. MessageBox. Show (string. Format ("{0}", Angle (button3Point, button2Point, button4Point )));
}