解题方法
1 . 已知在空间直角坐标系中,
,
,
,点
在平面
内,则
的最小值为______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b32ab04dd852329d5918b177c199eee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4511343c7a7c0d6bdf6a4d68f58a8c9d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/99b5c2937ee1515ae7fdad79834cfde4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8fe49a5474e1ff6b4fdc89794c1c96b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16f0b84ee4ed90face0993d4f4dda379.png)
您最近一年使用:0次
2 . 已知正方体
的棱长为
,
(
),现有如下四个命题:
①
,都有
;
②
,都存在
使得
;
③
,使得
;
④
的最小值为
.
其中所有真命题的序号是______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89f779d4fb6be5cea2641a0b39353363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2187ee1ea3b7e47a6283314322e5decf.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e43ceb80630415cf8260df5f1be3fa7d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/18db7868464d082ccc1998bd23bd6ab4.png)
②
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e43ceb80630415cf8260df5f1be3fa7d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6bb62f5043ccd21a6e020a41947b13f8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b391f64ed62db691e6c997f4cd90829d.png)
③
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5850edb7762a7e7e2c7f6d060916fd5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d55fbf13a2e7c1b406dc25f63424eab.png)
④
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cca201bc2c3144af7d0d2b18bf055d19.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36c3ab9b6089175ddcca69027a32e5c7.png)
其中所有真命题的序号是
您最近一年使用:0次