集合的等势 To make precise what it means for two sets (even two infinite sets)to have the same number of elements,we need a definition. We say that a set A is equivalent to a set B if there exists a bijection f:AB.We write A B for A is equivalent to B.(Other authors use the words equipotent or equinumerous. 问题2： 你原来脑海中的两个集合元素一样多”的概 念是什么样的呢？ 对无穷集合遁用吗？集合的等势