C# GMap: How to draw arc on a map

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;
}