public double EntranceTangentDirection {get;}

// iterate thru courses
foreach (var course in travParcel.Courses)
{
  var courseCOGOLine = course.COGOLine;

  var entranceTangentDir = course.EntranceTangentDirection;
  var exitTangentDir = course.ExitTangentDirection;

  // tangent to prior course if one of the following
  //     - defined with a ArcGIS.Desktop.Editing.COGO.TangentCurveDefinition
  //     - defined as a straight line defined with a 0 deflection angle.
  var isTangentToPriorCourse = course.IsDefinedAsTangentToPriorCourse;
  // IsTangent if one of the following
  //    - IsTangentToPriorCourse
  //    - is implied tangent - ie difference between entranceTangentDirection and previous courses ExitTangentDirection < tolerance
  var isTangent = course.IsTangent;
}