ArcGIS Pro 2.6 API Reference Guide
StartDirection Property
Example 

ArcGIS.Core.Geometry Namespace > GeodesicSectorParameter Class : StartDirection Property
Gets or sets the direction of starting radius of the sector as an angle in degrees.
Syntax
public double StartDirection {get; set;}
Public Property StartDirection As Double
Example
GeodesicSectorParameter param = new GeodesicSectorParameter();
param.ArcVertexCount = 50;
param.AxisDirection = Math.PI / 4;
param.Center = new Coordinate2D(0, 0);
param.LinearUnit = LinearUnit.Meters;
param.OutGeometryType = GeometryType.Polygon;
param.RadiusVertexCount = 10;
param.SectorAngle = 5 * Math.PI / 3;
param.SemiAxis1Length = 100000;
param.SemiAxis2Length = 20000;
param.StartDirection = 11 * Math.PI / 6;

Geometry geometry = GeometryEngine.Instance.GeodesicSector(param, SpatialReferences.WGS84);
// geometry.IsEmpty = false

Polygon polygon = geometry as Polygon;
// polygon.PointCount = 68
// polygon.PartCount = 1
Requirements

Target Platforms: Windows 10, Windows 8.1, Windows 7

See Also

Reference

GeodesicSectorParameter Class
GeodesicSectorParameter Members