The fundamental group of \(X\) at \(x_0\) is \[\pi_1(X, x_0) \;:=\; \bigl\{[\gamma] \mid \gamma \text{ is a loop based at } x_0\bigr\}\] equipped with the group operation of concatenation: \[[\gamma] \cdot [\delta] := [\gamma * \delta], \qquad (\gamma * \delta)(s) := \begin{cases} \gamma(2s) & s \in [0,\tfrac{1}{2}] \\ \delta(2s-1) & s \in [\tfrac{1}{2},1] \end{cases}\] The identity element is the class of the constant loop \([c_{x_0}]\), and the inverse of \([\gamma]\) is \([\bar\gamma]\) where \(\bar\gamma(s) := \gamma(1-s)\).
Нина Ташевская (Редактор отдела «Среда обитания»)
，推荐阅读WPS官方版本下载获取更多信息
<dependency
（五）自带行李，是指旅客自行携带、保管或者放置在客舱中的行李。
人力资源社会保障部数据显示，2025年全国城镇新增就业1267万人，城镇调查失业率均值为5.2%，就业形势保持总体稳定。