名校
解题方法
1 . 在四棱锥
中,底面
为菱形,
,平面
平面
.
![](https://img.xkw.com/dksih/QBM/2021/10/12/2827654495502336/2832132390297600/STEM/e7724b17d8404948b2ddf89f630f3bd7.png?resizew=207)
(1)求四棱锥
的体积;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ebfcf34539673d516eb9b259951a81ed.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/672b012a2d118ad3d8aeeac54092a552.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8704811c9c5dba854310ae0de2ba6b05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://img.xkw.com/dksih/QBM/2021/10/12/2827654495502336/2832132390297600/STEM/e7724b17d8404948b2ddf89f630f3bd7.png?resizew=207)
(1)求四棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ebfcf34539673d516eb9b259951a81ed.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/160506ba62e181c946b0c8fc31d0d956.png)
您最近一年使用:0次
2 . 已知三棱锥
中,
,
是边长为
的正三角形,
,
分别是
,
的中点,
,则以下说法正确的是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/30fc65a72853bd8ac1ad0828270d3baf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a33f381b03270154695d6b5421b1e739.png)
A.![]() |
B.![]() ![]() ![]() |
C.此三棱锥外接球的体积是![]() |
D.此三棱锥的表面积与它的外接球的表面积的比值为![]() |
您最近一年使用:0次