解题方法
1 . 如图,在四棱锥
(图一)和三棱锥
(图二)中,四边形
为正方形,
平面
,
≌
,将四棱锥
和三棱锥
重新组合成一个新的几何体(图三),且面
和面
完全重合,且
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/17/484436c0-9d40-48c2-a9e9-8517e1310270.png?resizew=480)
(1)证明:
平面
;
(2)求四棱锥
的体积与组合后的几何体的体积比.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55c6caa0455442437177ab9b995df37b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9deb96336e49627dff7bfaf36623b941.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6358776bf61b2f84d329c310ac9b96be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/900e90179062ff6cb33f58d361aedf5d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/217d37ca5469a57cb7417a2ac0d58efe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55c6caa0455442437177ab9b995df37b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9deb96336e49627dff7bfaf36623b941.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21c133b31ab3c50dc87d80879bbb0633.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bed4f6bd8368c262808d798dd3747f35.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48901f9b0ee1e3c2b766bf908f4da30f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/307d88c54b47edca0308cea049965732.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/17/484436c0-9d40-48c2-a9e9-8517e1310270.png?resizew=480)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b61346bd4091070ba84a4046f87f365.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9111c8e64fc183a777dbe0e82c9202cd.png)
(2)求四棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55c6caa0455442437177ab9b995df37b.png)
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