1 . 如图,在四面体
中,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40bdf4b769034a94e4a488148d5bf25.png)
,二面角
是直二面角,
为
的中点,点
为线段
上一点,且
.
![](https://img.xkw.com/dksih/QBM/2021/2/25/2665851876081664/2671194726326272/STEM/cccdaa438e8b4fd489ccecca8c441778.png?resizew=189)
(1)求证:
平面
;
(2)求平面
与平面
所成锐二面角的平面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40bdf4b769034a94e4a488148d5bf25.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5336fe7dd901d5555ba705f78020fc98.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f1854ba6cc92481d7a616bd2788a47e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58ac6979adfa3b30c6067a9fdfd49f08.png)
![](https://img.xkw.com/dksih/QBM/2021/2/25/2665851876081664/2671194726326272/STEM/cccdaa438e8b4fd489ccecca8c441778.png?resizew=189)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2ffc6952e988d04f22f0fb2f7f0ab7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/828fcf6ed16b5dae1b572d471f5ed7a7.png)
(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/828fcf6ed16b5dae1b572d471f5ed7a7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4eb7e9ad5486cf1c5e506b20c5469e8.png)
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2021-03-05更新
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123次组卷
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2卷引用:西藏林芝市、日喀则市2021届高三下学期第一次联考数学(理)试题