1 . 如图1,在边长为4的等边三角形ABC中,D,E,F分别是AB,AC,BC的中点,沿DE把
折起,得到如图2所示的四棱锥.
![](https://img.xkw.com/dksih/QBM/2022/1/7/2889217549983744/2889834336264192/STEM/760fd5e4-f343-440f-ba9a-0cb27f3e2cb5.png?resizew=292)
(1)证明:
平面
.
(2)若二面角
的大小为60°,求平面
与平面
的夹角的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://img.xkw.com/dksih/QBM/2022/1/7/2889217549983744/2889834336264192/STEM/760fd5e4-f343-440f-ba9a-0cb27f3e2cb5.png?resizew=292)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/06222ee533c2484ab25321a6abbf98cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7935fe3125f247b7bea4f065ce9ad985.png)
(2)若二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/628d6fc46c651e0c783b81a123a7b229.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9afac7c616bbb14e1ed428a3c507c7dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f233b375753611ffa7a93c2c12ef5e28.png)
您最近一年使用:0次
2022-01-08更新
|
1101次组卷
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5卷引用:吉林省白山市2021-2022学年高二上学期期末数学试题
吉林省白山市2021-2022学年高二上学期期末数学试题甘肃省白银市靖远县2021-2022学年高二上学期期末数学(理)试题甘肃省庆阳市2021-2022学年高二上学期1月月考数学(理)试题辽宁省辽阳市2021-2022学年高二上学期期末考试数学试题(已下线)三省三校2022届高三下学期第一次模拟数学(理)试题变式题16-20
名校
解题方法
2 . 如图,在四棱锥
中,底面
是正方形,侧面
是边长为2的正三角形,
,点
为线段
的中点,点
是
上的点.
![](https://img.xkw.com/dksih/QBM/2020/12/9/2610614247284736/2613496238653440/STEM/e1b21a4f2b1e4290b9cd2fdb937aefd5.png?resizew=246)
(1)当
为
中点时,证明:平面
平面![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f747eb5b2d21c9de962cbfd4ec4bb7.png)
(2)当
时,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37002ada5d194d4d062fa3285d7d9824.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://img.xkw.com/dksih/QBM/2020/12/9/2610614247284736/2613496238653440/STEM/e1b21a4f2b1e4290b9cd2fdb937aefd5.png?resizew=246)
(1)当
![](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/5f6dd051db98c531f9ef18cdfd793f4a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f747eb5b2d21c9de962cbfd4ec4bb7.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/298c5ddd29b64067b9f40b21f2d2580c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/90e7ecb1eb5528dbfe9492f516aae609.png)
您最近一年使用:0次
2020-12-13更新
|
725次组卷
|
4卷引用:吉林省白山市2020-2021学年高三上学期期末数学试题