东北数学（英文版）
東北數學（英文版）
동북수학（영문판）
NORTHEASTERN MATHEMATICAL JOURNAL
2004年
1期
84-88
,共5页
Helly number%parallel triangle%line transversal%convex set%right triangle%obtuse triangle%acute triangle
We prove two results about the problem of finding the Helly number for line transversals to a family of parallel triangles in the plane: (1) If each three triangles of a family of parallel right triangles are intersected by an ascending (or a descending) line, then there is an ascending (or a descending) line that intersects all the triangles of the family; (2) If each three triangles of a family of parallel obtuse triangles are intersected by an ascending (or a descending) line, then there is an as cending (or a descending) line that intersects all the triangles of the family. We also obtain that the Helly number of a family of parallel right or obtuse triangles is 3.
