1 . 如图,在三棱柱
中,平面
平面
,侧面
为平行四边形,侧面
为正方形,
,
,
为
的中点.
![](https://img.xkw.com/dksih/QBM/2020/4/4/2434445427367936/2435828026286080/STEM/fe2aedc59e2e410c95cf447c6c610e34.png?resizew=271)
(1)求证:
平面
;
(2)求二面角
的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/02cfa6b4db3a67fcd3c169fd8502a66d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cf9a6db3571fa57bfa2d5e4d44c51b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2dde327febef2331a4766a79b433cc02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2dde327febef2331a4766a79b433cc02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/822ba132ca9dd0d4a050659aef3c9b26.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f393a0ff5f01a41e1f4c9cfd723adeb6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/00bab17635a999236e8d2e35017a208d.png)
![](https://img.xkw.com/dksih/QBM/2020/4/4/2434445427367936/2435828026286080/STEM/fe2aedc59e2e410c95cf447c6c610e34.png?resizew=271)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ac39b7f1de83c517272fddb54caec27.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/af68a7bf0da4f7c6f739d2e2461ad9b7.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ecab298d6d029b091e283f24c78f03be.png)
您最近一年使用:0次
2 . 已知等腰梯形
,
.现将
沿着
折起,使得面
面
,点F为线段BC上一动点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/2/585ac82a-3cff-4d74-93f0-fdd20dac6219.png?resizew=338)
(1)证明:
;
(2)如果F为BC中点,证明:
面
;
(3)若二面角
的余弦值为
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d6c116afaf8619f0a722883615429943.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1abcad002e8d35c72f3f96bd6244c17f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cc3814287dbb60d478bffc5366f9928b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed5f0cfc1049f84a04c81bd213afb8d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d6bfad3f7e65188bcf7f62ea5acdbf4a.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/2/585ac82a-3cff-4d74-93f0-fdd20dac6219.png?resizew=338)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f64912cf9f1bccc365532ab1cb26481a.png)
(2)如果F为BC中点,证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/40f44f2b2f82a9126223138972850aa2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c09afc70f448545336304333d5b5658b.png)
(3)若二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0f1592b2ad60fa438c2564ff651231f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dac452fbb5ef6dd653e7fbbef639484.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72acf5ee54c89dede4358c61ecd7a101.png)
您最近一年使用:0次
3 . 如图,在四棱锥
中,底面
是菱形,
,
平面
,
,
,
,
是
中点.
(1)求证:直线
平面
.
(2)求证:直线
平面
.
(3)在
上是否存在一点
,使得二面角
的大小为
,若存在,确定
的位置,若不存在,说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd7a42341edbc0b01ab0769c4c02c3e3.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/b366eb3c3c2c1e7be9c0d52d770ee1f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8676b624f105072a3185911b25c912dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb4f47cccdb7195f15858fcfdf644214.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
(1)求证:直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9f33fa5152ba27f7b8a28890cefca219.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d62de810f5160223afa54fd882acb9b.png)
(2)求证:直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97f30533da2e1d2a958dc906c37eba9d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b37793a3a810e823e10c340986f55ddd.png)
(3)在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad650e9f39ef57d26c81ec8f414f2c22.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d88591679796c52024d11c4de641bdb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/2/62fda40a-1a90-4e45-80f3-f64ba6a10355.png?resizew=173)
您最近一年使用:0次