1 . 《九章算术》中,将底面为长方形且有一条侧棱与底面垂直的四棱锥称之为阳马,将四个面都为直角三角形的四面体称之为鳖臑.
如图,在阳马
中,侧棱
底面
,且
,
为
中点,点
在
上,且
平面
,连接
,
.
![](https://img.xkw.com/dksih/QBM/2017/4/6/1659802709663744/1659993639682048/STEM/3963f6aa-d17c-4424-9f25-748a1acdd1c7.png?resizew=260)
(Ⅰ)证明:
平面
;
(Ⅱ)试判断四面体
是否为鳖臑,若是,写出其每个面的直角(只需写出结论);若不是,说明理由;
(Ⅲ)已知
,
,求二面角
的余弦值.
如图,在阳马
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5a1b49f64e0065edad868b25e9fcada3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37e2267c84394668eff2e9f5918de4fb.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/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c45fbffb9e2c7fa7c5006cde8da0cabe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/134ef0b1a2669a09f05bd4dc2496f706.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://img.xkw.com/dksih/QBM/2017/4/6/1659802709663744/1659993639682048/STEM/3963f6aa-d17c-4424-9f25-748a1acdd1c7.png?resizew=260)
(Ⅰ)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8d2d217e9bcd059908f117dfc4d4259.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
(Ⅱ)试判断四面体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dfc50ecfa45216f8d098662452cf8d08.png)
(Ⅲ)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09d27bd71d79cb19eb554175e4ef0867.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d79e7020414add95907e061df505ef0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4a78d0c03cfa2b17832b629a5c2f1be.png)
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2017-04-06更新
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2卷引用:2017届北京市石景山区高三3月统一练习数学理试卷