名校
1 . 已知四面体
的所有棱长均为
,
分别为棱
的中点,
为棱
上异于
的动点.有下列结论:
①线段
的长度为
; ②点
到面
的距离范围为
;
③
周长的最小值为
; ④
的余弦值的取值范围为
.
其中正确结论的个数为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7789a500686c7a73770404ead6af0590.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d93949d8a15aca4e79cedb978590571.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
①线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bdaa19de263700a15fcf213d64a8cd57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/412ef8edcf697ce9606cf82f58d695f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2b351ac1e1ee3320fc5bd49db86cade8.png)
③
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ecfb02e157819a2bdd0f2790cbc825e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f190b17530d81d927c358ac84757a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e07505530a9ec2f9c8a23e3c9eafa313.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f10de03f6c562a5b05a6fd8a0cbd290.png)
其中正确结论的个数为( )
A.![]() | B.![]() | C.![]() | D.![]() |
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