1 . 如图,已知三棱柱
的所有棱长均为
,平面
平面
,
,
为
的中点.
![](https://img.xkw.com/dksih/QBM/2018/4/27/1933157871656960/1936064367230976/STEM/65e373834b37435ebaf6547f654e0d9f.png?resizew=167)
(1)证明:
;
(2)若
是棱
的中点,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3d7090639341730951c1bc3c9b6164e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e9edc50f7febbc2d5d8dcdc23a3630a7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f68ce09db7cb705ab0a43ecf17748e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d88bf46ad08f9677c37eed1d0369329.png)
![](https://img.xkw.com/dksih/QBM/2018/4/27/1933157871656960/1936064367230976/STEM/65e373834b37435ebaf6547f654e0d9f.png?resizew=167)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04cb9dcf55e30f777ae74fe44e7d1732.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c632eabdaa95f4e9d7fca582218e49e.png)
您最近一年使用:0次
2017-09-19更新
|
782次组卷
|
4卷引用:河南省豫北豫南名校2018届高三上学期精英联赛数学(理)试题
解题方法
2 . 如图,在三棱柱
中,
是
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/5/0165774f-225f-4557-afa7-056fea9613d2.png?resizew=169)
(1)求证:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d8772aa893a9c1d40f714cb25701701.png)
平面
;
(2)若
,求证
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/5/0165774f-225f-4557-afa7-056fea9613d2.png?resizew=169)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d8772aa893a9c1d40f714cb25701701.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/638537c0a30676c73fea76c80e0f8bd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/74bca84ad86c648d3bb20c8909c8da3f.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c287bb15494297df234f700f9f3a90d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fffbf41f3890efb6956907ad3c4062a0.png)
您最近一年使用:0次
3 . 如图,在三棱柱
中,
为
的重心,
.
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/4107b0d1923d45b09238bc09a28452fe.png)
(1)求证:
平面
;
(2)若侧面
底面
,
,
,求直线
与平面
所成角
的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ec23977096e2408f069d182cbb84952.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/4107b0d1923d45b09238bc09a28452fe.png)
(1)求证:
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/0a2d96eb15f34ca797d4cdaae020b3e4.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/3534f11d09ae4ce1b494c0718bf5ef7e.png)
(2)若侧面
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/f130827cc656411b859d442fb13214b8.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/4314e28a5a724d8a82ad4a475a7835c8.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/3203f71d7f474c6eb733c09448d39abc.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/3626d78e70e44179a42520742d11e675.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/477fb6aa067941f59eeab728f3f339d9.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/2634291559384aa89d9326d2dddfe1e5.png)
![](https://img.xkw.com/dksih/QBM/2016/12/29/1619414854590464/1619414855147520/STEM/c47a0a731edf453086a2e2f5e221508a.png)
您最近一年使用:0次