设S为复数集C的非空子集.若对任意
,都有
,则称S为封闭集.下列命题:
①集合S={a+bi|(
为整数,
为虚数单位)}为封闭集;
②若S为封闭集,则一定有
;
③封闭集一定是无限集;
④若S为封闭集,则满足
的任意集合
也是封闭集.
上面命题中真命题共有哪些?
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c36aecba41f6f5ff0d46a29dccaaf01.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ced3ae86527d84d5cfc6f78eaa33de24.png)
①集合S={a+bi|(
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/632244ea6931507f8656e1cc3437d392.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c05b9832b09731a574d4a4adf7448de.png)
②若S为封闭集,则一定有
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1330666c9b3d23a6fd9b25380270a1a9.png)
③封闭集一定是无限集;
④若S为封闭集,则满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f0e8b1ffee974f4cb6afc2cfd8220fa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b68df477b3ee45ac0f725db00d465a1.png)
上面命题中真命题共有哪些?
A.![]() ![]() ![]() ![]() ![]() ![]() | B.①②③ | C.①②④ |
更新时间:2019-01-30 18:14:09
|
【知识点】 集合新定义
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A.对于任意集合![]() ![]() |
B.若![]() ![]() |
C.若![]() ![]() |
D.若![]() ![]() |
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