Code

bool Intersect(Arrow a1, Arrow a2)
{
 PointF pt = PointF.Empty;
 PointCollection points1 = a1.ControlPoints;
 PointCollection points2 = a2.ControlPoints;

 for (int i = 0; i < points1.Count - 1; i++)
 {
  for (int j = 0; j < points2.Count - 1; j++)
  {
   PointF k1 = points1[i];
   PointF k2 = points1[i + 1];
   PointF l1 = points2[i];
   PointF l2 = points2[i + 1];

   if (Utilities.segmentIntersect(k1, k2, l1, l2, ref pt))
    return true;
  }
 }

 return false;
}