2013年1月16日
数学分析原理习题第二章
摘要： 1. prove that the empty set is a subset of every set. for a element x in a empty set, x is null , so x is a element of every other set since x is null... 阅读全文
posted @ 2013-01-16 15:59 StanleyWu 阅读(1029) 评论(0) 推荐(0) 编辑