1 . 如图,
垂直圆O所在的平面,
是圆O的一条直径,C为圆周上异于A,B的动点,D为弦
的中点,
.
![](https://img.xkw.com/dksih/QBM/2020/3/17/2421426660630528/2422388807286784/STEM/04572f2438e841a0a873e3de4d225b1a.png?resizew=136)
(1)证明:平面
平面
;
(2)若
,求平面
与平面
所成锐二面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef49a3ca580a144cc65a609c167facc1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f430358028a58cc34567deae961696fe.png)
![](https://img.xkw.com/dksih/QBM/2020/3/17/2421426660630528/2422388807286784/STEM/04572f2438e841a0a873e3de4d225b1a.png?resizew=136)
(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3da05ded8b60b97142b4d975ffe782c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/771b610e4ddefa739a985d1e5462ce5a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0628681907ac8d7fdb94d8bc1b15feb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c15b63176f43bc7a0654d0f6f45e7429.png)
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2020-03-18更新
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204次组卷
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2卷引用:河北省邯郸市六校2019届高三上学期期中大联考数学(理科)试题