名校
1 . 棱长为4的正方体
中,E,F分别为棱
,
的中点
,则下列说法中正确的有__________ (填写所有正确结论的序号)
① 三棱锥
的体积为定值
②当
时,平面
截正方体所得截面的周长为![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ff1a96915dbc74998f363ae71c451964.png)
③ 直线FG与平面
所成角的正切值的取值范围是![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11c24a948697acd85514e84c31eec3d0.png)
④ 当
时,三棱锥
的外接球的表面积为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/394c5d2f55221975503be8aa18022480.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/076b1c6a8e9cc91c0d70fc4b082cbadb.png)
① 三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3e01c3c6573415116f03ea680fdcaf7.png)
②当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac1c3ea872a20fdc1843cb5ffce8a554.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f463ce7839e5e952fd5a4650b658ace.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ff1a96915dbc74998f363ae71c451964.png)
③ 直线FG与平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e168672b47d7e64dc1b404f8882c7dcf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11c24a948697acd85514e84c31eec3d0.png)
④ 当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8845fadc307f1d308410e829becedd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e79d516856d92c60553659a22a45118e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60947b942a059885a1c01218604fbcb6.png)
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