C# GMap: How to draw arc on a map

Question

Hello, how can I add a polygon to the map as in the picture below? From a certain point of coordinates should open a polygon long, for example, 1 kilometer and a 120-degree opening angle.

 

My code can only draw a circle. Can it be changed so that it can draw a polygon from a certain point of coordinates with an indication of the direction, distance of drawing and the angle of aperture?

 

private void CreateCircle(Double lat, Double lon, double radius, int ColorIndex) {
 GMapOverlay markers = new GMapOverlay(mygmap, "markers");
 PointLatLng point = new PointLatLng(lat, lon);
 int segments = 1080;

 List < PointLatLng > gpollist = new List < PointLatLng > ();

 for (int i = 0; i < segments; i++) {
  gpollist.Add(FindPointAtDistanceFrom(point, i * (Math.PI / 180), radius / 1000));
 }

 GMapPolygon polygon = new GMapPolygon(gpollist, "Circle");
 switch (ColorIndex) {

  case 1:
   polygon.Fill = new SolidBrush(Color.FromArgb(80, Color.Red));
   break;
  case 2:
   polygon.Fill = new SolidBrush(Color.FromArgb(80, Color.Orange));
   break;
  case 3:
   polygon.Fill = new SolidBrush(Color.FromArgb(20, Color.Aqua));
   break;
  default:
   MessageBox.Show("No search zone found!");
   break;
 }

 polygon.Stroke = new Pen(Color.Red, 1);
 markers.Polygons.Add(polygon);
 mygmap.Overlays.Add(markers);
}

public static GMap.NET.PointLatLng FindPointAtDistanceFrom(GMap.NET.PointLatLng startPoint, double initialBearingRadians, double distanceKilometres) {
 const double radiusEarthKilometres = 6371.01;
 var distRatio = distanceKilometres / radiusEarthKilometres;
 var distRatioSine = Math.Sin(distRatio);
 var distRatioCosine = Math.Cos(distRatio);

 var startLatRad = DegreesToRadians(startPoint.Lat);
 var startLonRad = DegreesToRadians(startPoint.Lng);

 var startLatCos = Math.Cos(startLatRad);
 var startLatSin = Math.Sin(startLatRad);

 var endLatRads = Math.Asin((startLatSin * distRatioCosine) + (startLatCos * distRatioSine * Math.Cos(initialBearingRadians)));
 var endLonRads = startLonRad + Math.Atan2(Math.Sin(initialBearingRadians) * distRatioSine * startLatCos, distRatioCosine - startLatSin * Math.Sin(endLatRads));

 return new GMap.NET.PointLatLng(RadiansToDegrees(endLatRads), RadiansToDegrees(endLonRads));
}

public static double DegreesToRadians(double degrees) {
 const double degToRadFactor = Math.PI / 180;
 return degrees * degToRadFactor;
}

public static double RadiansToDegrees(double radians) {
 const double radToDegFactor = 180 / Math.PI;
 return radians * radToDegFactor;
}