名校
1 . 已知三棱柱
中,
,
是
的中点,
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/26/dff8f8c3-b2fb-4ef3-b490-c205bb1e2700.jpg?resizew=224)
(1)求证:
;
(2)若侧面
为正方形,求直线
与平面
所成角的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4639a9dc0bc99101cbde59fef04b4a2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f00f9d78c6df49f58a527aac02be39d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0acdac99ea95c00e80fbf49941ba2803.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/26/dff8f8c3-b2fb-4ef3-b490-c205bb1e2700.jpg?resizew=224)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36c4559d27e3905980d1a4f1856f07de.png)
(2)若侧面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d9a8181f7a7fe7f3fac872ce9534f15.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87cdc08e1c4a04a18d5ecea03393e36d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c2ce0eeb7a6d6c7806cf2352b9fe15c2.png)
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2 . 如图,在四棱锥
中,平面PAD垂直平面ABCD,底面
为平行四边形,已知
,
,
于
.
![](https://img.xkw.com/dksih/QBM/2018/4/9/1920593447059456/1920893169713152/STEM/f8f142d2576848918b371d476d46eb34.png?resizew=175)
(1)求证:
;
(2)若平面
平面
,且
,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d02bd5cfe804460846423e77f72db10f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5cb3f9a5da641be35117fd35ba07a6aa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/644ec7c3e0d9472da97a78fe7b004a88.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bba1c6851a385f34214677113d04ffa9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f9df6a61c453b50f0fea4f4f640df45c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://img.xkw.com/dksih/QBM/2018/4/9/1920593447059456/1920893169713152/STEM/f8f142d2576848918b371d476d46eb34.png?resizew=175)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1030483a875845da3d8bdeead1c41ecd.png)
(2)若平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ebbb79892c8cb8871a08437acc09bc80.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5cb3f9a5da641be35117fd35ba07a6aa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/337421403f59eb20bdc8b446691f8a18.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89dead99c372e7947e7337dfc4d2a7e1.png)
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