名校
解题方法
1 . 已知集合
,且
,则( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9eacc1dab08f4853ac7516ba3a27c4c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/999c373e25c3502c0380986a4a3e66c3.png)
A.![]() | B.![]() |
C.![]() ![]() | D.![]() |
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2 . 拓扑学是一个研究图形(或集合)整体结构和性质的一门几何学,以抽象而严谨的语言将几何与集合联系起来,富有直观和逻辑.已知平面
,定义对
,
,其度量(距离)
并称
为一度量平面.设
,
,称平面区域
为以
为心,
为半径的球形邻域.
(1)试用集合语言描述两个球形邻域的交集;
(2)证明:
中的任意两个球形邻域的交集是若干个球形邻域的并集;
(3)一个集合称作“开集”当且仅当其是一个无边界的点集.证明:
的一个子集是开集当且仅当其可被表示为若干个球形邻域的并集.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15e7cbf6370f2b5c37816278c4d52324.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cd50ba95ce394ae2cc7d8953268cad4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/528fd55bccdd48b002249e27153164dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/84e93599300cd0cc2ee3747a0a1a01a1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/331b36f89fa4fc1a314bd2fb469b6756.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f853b9d71837401854312c2a3a2012d0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/663819fd38d196961788cad4e2e039a1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/77c4e98464e40174ae21e741ae79dea5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/678bfef0c3cf7ee6438c64d20ab44617.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd934b73981f16a85a9a9d6554ec9791.png)
(1)试用集合语言描述两个球形邻域的交集;
(2)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba1985327691201a2fbcbb27689f2015.png)
(3)一个集合称作“开集”当且仅当其是一个无边界的点集.证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba1985327691201a2fbcbb27689f2015.png)
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