设https://bgk-photo.cdn.bcebos.com/b64543a98226cffc4c4814d2a9014a90f603ea74.jpg是https://bgk-photo.cdn.bcebos.com/728da9773912b31beb0e66499618367adab4e174.jpg中的有界闭集, https://bgk-photo.cdn.bcebos.com/267f9e2f07082838746f7774a899a9014c08f174.jpg,证明https://bgk-photo.cdn.bcebos.com/2cf5e0fe9925bc31b0e0aaf84edf8db1cb137015.jpg为有界闭集.举例说明当https://bgk-photo.cdn.bcebos.com/35a85edf8db1cb13b8d49773cd54564e92584b15.jpg无界时,https://bgk-photo.cdn.bcebos.com/d058ccbf6c81800ae458226ea13533fa828b4715.jpg可以不是闭集.
设https://bgk-photo.cdn.bcebos.com/b64543a98226cffc4c4814d2a9014a90f603ea74.jpg是https://bgk-photo.cdn.bcebos.com/728da9773912b31beb0e66499618367adab4e174.jpg中的有界闭集, https://bgk-photo.cdn.bcebos.com/267f9e2f07082838746f7774a899a9014c08f174.jpg,证明https://bgk-photo.cdn.bcebos.com/2cf5e0fe9925bc31b0e0aaf84edf8db1cb137015.jpg为有界闭集.举例说明当https://bgk-photo.cdn.bcebos.com/35a85edf8db1cb13b8d49773cd54564e92584b15.jpg无界时,https://bgk-photo.cdn.bcebos.com/d058ccbf6c81800ae458226ea13533fa828b4715.jpg可以不是闭集.
发布时间：2025-08-12 23:01:08
,
互异点列
,由于
是有界闭集, 
,
,故
,
,显然
,可见
,于是
,所以
是闭集.(2)取
,
,
,显然
是
中的无界闭集,下面研究
.
,
显然
,
,而
可见
不是闭集.习题2-3-P42P42
