2012高二·甘肃天水·学业考试
名校
1 . 如图,已知四棱锥
的底面
是菱形,
平面
,
,点
为
的中点.
(1)求证:
平面
;
(2)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/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/931451b2a6983bd8f640932dca5acf05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/8/17/78ac39f0-23c1-4c34-898e-196b4af199b2.png?resizew=177)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8c2b786c64e6a9ed2ec5670cde74f86.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9efe66d99f813c6b1387392186822bb.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6967e3578fc16fc4baf0898f83be3da0.png)
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5卷引用:2011-2012学年甘肃省天水一中高二第二次学业水平测试数学试卷