public void QueryCoords( 
   out Coordinate2D centerCoordinate,
   out double startAngle,
   out double centralAngle,
   out double rotationAngle,
   out double semiMajorAxis,
   out double semiMinorAxis
)

{
  // Construct a circle with center at (-1,-1), radius = 2, and oriented clockwise.
  // Use a builderEx convenience method or use a builderEx constructor.

  Coordinate2D centerPtCoord = new Coordinate2D(-1, -1);

  // Builder convenience methods don't need to run on the MCT.
  EllipticArcSegment circle = EllipticArcBuilderEx.CreateCircle(centerPtCoord, 2, ArcOrientation.ArcClockwise);
  // circle.IsCircular = true
  // circle.IsCounterClockwise = false
  // circle.IsMinor = false

  double startAngle, rotationAngle, centralAngle, semiMajor, semiMinor;
  Coordinate2D actualCenterPt;
  circle.QueryCoords(out actualCenterPt, out startAngle, out centralAngle, out rotationAngle, out semiMajor, out semiMinor);

  // semiMajor = 2.0
  // semiMinor = 2.0
  // startAngle = PI/2
  // centralAngle = -2*PI
  // rotationAngle = 0
  // endAngle = PI/2

  // This EllipticArcBuilderEx constructor doesn't need to run on the MCT.
  EllipticArcBuilderEx builder = new EllipticArcBuilderEx(centerPtCoord, 2, ArcOrientation.ArcClockwise);
  EllipticArcSegment otherCircle = builder.ToSegment();
}

{
  // retrieve the curve's control points
  EllipticArcSegment arc = EllipticArcBuilderEx.CreateEllipticArcSegment(ellipticArcSegment);
  MapPoint startPt = arc.StartPoint;
  MapPoint endPt = arc.EndPoint;
  Coordinate2D centerPt = arc.CenterPoint;
  bool isCircular = arc.IsCircular;
  bool isMinor = arc.IsMinor;
  bool isCounterClockwise = arc.IsCounterClockwise;
  bool isCurve = arc.IsCurve;
  double len = arc.Length;
  double ratio = arc.MinorMajorRatio;

  double semiMajorAxis, semiMinorAxis;
  // get the axes
  arc.GetAxes(out semiMajorAxis, out semiMinorAxis);
  // or use the properties
  // semiMajorAxis = arc.SemiMajorAxis;
  // semiMinorAxis = arc.SemiMinorAxis;

  double startAngle, centralAngle, rotationAngle;
  // or use QueryCoords to get complete information
  arc.QueryCoords(out centerPt, out startAngle, out centralAngle, out rotationAngle, out semiMajorAxis, out semiMinorAxis);

  // use properties to get angle information
  //double endAngle = arc.EndAngle;
  //centralAngle = arc.CentralAngle;
  //rotationAngle = arc.RotationAngle;
  //startAngle = arc.StartAngle;
}