1 . 如图,等边三角形
所在平面与梯形
所在平面互相垂直,且有
,
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/7/91521f4b-8068-48a6-815e-d16d892fa130.png?resizew=168)
(1)证明:平面
平面
;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0628681907ac8d7fdb94d8bc1b15feb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0facf189b2a3153beb7b9e077d3b1146.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/46eb2323492e8d720a014c0ad3c4d476.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e65a3e478bb87d094e3a0af30dd10ae8.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/7/91521f4b-8068-48a6-815e-d16d892fa130.png?resizew=168)
(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e4aa9084b8fe0fe05c4388d1f835587b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0628681907ac8d7fdb94d8bc1b15feb9.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1069d514c3c32aeabd274475ee209ed6.png)
您最近一年使用:0次
13-14高三·江西·期末
名校
2 . 如图,在四棱锥
中,底面
是正方形,
底面
,
,点
是
的中点,
,交
于点
.
![](https://img.xkw.com/dksih/QBM/2014/2/27/1571532730245120/1571532736012288/STEM/99aef7236a9647888aba9e7ad41cf8b8.png)
(1)求证:平面
平面
;
(2)求三棱锥
的体积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5aa0d36da718de7c50a781b8e2bb8e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/198b300533b4d6cc3d5b76a9b9133a11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c3d38ef2cde6b676f097c7578f05d753.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/defa5b53043ae802bb1af7d14374406d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1d677b24337accc0b29bf50709185128.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c2bc5e50b8dfa02601c70822252854a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://img.xkw.com/dksih/QBM/2014/2/27/1571532730245120/1571532736012288/STEM/99aef7236a9647888aba9e7ad41cf8b8.png)
(1)求证:平面
![](https://img.xkw.com/dksih/QBM/2014/2/27/1571532730245120/1571532736012288/STEM/a24bf5a214e5454785112e6a0b58de40.png)
![](https://img.xkw.com/dksih/QBM/2014/2/27/1571532730245120/1571532736012288/STEM/f9143803559c4e2985d230de84cc1f49.png)
(2)求三棱锥
![](https://img.xkw.com/dksih/QBM/2014/2/27/1571532730245120/1571532736012288/STEM/ca12076cb4114295a5e0fb9eb0f864a8.png)
您最近一年使用:0次