reachable set

例句：

1. 1. In mathematics, a reachable set is a subset of a set that can be reached from any point in the set by moving along a straight line.
   在数学中，一个可达集合是某个集合的子集，从集合中的任何一点沿着直线移动都可以到达。
2. 2. The problem with this definition is that it doesn't account for the fact that some elements in theset are not reachable from any other element.
   这个定义的问题是它没有考虑到集合中有些元素不能从其他元素到达的事实。
3. 3. To solve this problem, we need to define a new concept called a "reachable set" that includes all elements in the original set and allows for movement along lines that connect the elements.
   为了解决这个问题，我们需要定义一个新的概念叫做“可达集合”，它包括原始集合中的所有元素，并允许沿着连接元素的线进行移动。