private void CalculateArc()
{
this.CoordinateSystem = CoordinateSystem.Destination;
_arc.CoordinateSystem = CoordinateSystem.Destination;
// The arc center is the vertex of the protractor
_arc.Location = this.Points[1];
_arc.InvariantTopLeft = new PointF(-_arcRadius, -_arcRadius);
_arc.InvariantBottomRight = new PointF(_arcRadius, _arcRadius);
float startAngle, sweepAngle;
CalculateAngles(out startAngle, out sweepAngle);
_arc.StartAngle = startAngle;
_arc.SweepAngle = sweepAngle;
_arc.ResetCoordinateSystem();
this.ResetCoordinateSystem();
}
