public void Case3(Sink sink, Edge edge, Trapezoid[] tList)
{
YNode yNode = new YNode(edge, Sink.Isink(tList[0]), Sink.Isink(tList[1]));
Replace(sink, yNode);
}
private Trapezoid Locate(Edge edge)
{
return(_head.Locate(edge).Trapezoid);
}