set of fixed points的用法和樣例：
例句
- In this paper, we study the minimum-weight feedback vertex set problem in outerplanar graphs and present a linear time algorithm to solve it.
本文主要考慮外平面圖中的反饋點集並給出了一個求外平面圖最小頂點賦權反饋點集的線性時間演算法。 - The third part is to proof theimpaction set is finite.Comparing Hamiltonian systems without impacts, we should use a technical codition.
相對於沒有碰撞的哈密頓系統而言，我們為了證明碰撞點集是有限集而加入了一些技術性條件。
