在四棱锥
中,
,
,
为
中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/26/6f7607a1-7171-4139-a07b-919dee22eb7d.png?resizew=171)
(1)证明:
平面
;
(2)若
,
,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/faeb97acf19bd3b2c6c77c2814df4d2f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f121eabff3c62c1a196d9ca5f6f83f0b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e6864668d1c79964330e07e8f442569.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/defa5b53043ae802bb1af7d14374406d.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/26/6f7607a1-7171-4139-a07b-919dee22eb7d.png?resizew=171)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c8fcf28ce826ee6c876a00017dc4623.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc9c9cfa597b444b5c9dbae7a825a695.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32fef1452348d9c2c72343ba5210bd69.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72d29b82af44ff3180d17db67f8c0fa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/517414a784241b5285f015ecca85681d.png)
更新时间:2020-03-28 19:45:59
|
相似题推荐
解答题-证明题
|
适中
(0.65)
名校
【推荐1】如图,在三棱柱
中,
,底面为正三角形,
,D是BC的中点,P是
的中点.求证:
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/27/5b9c3d48-2d88-42ad-91a8-252d8cbf26cd.png?resizew=124)
(1)
平面
;
(2)
平面
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cc61a2aa5d8aebe6773d235f31ed81f0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1baa3d0db9ad31d33c2883a6efed1dc7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d88bf46ad08f9677c37eed1d0369329.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/27/5b9c3d48-2d88-42ad-91a8-252d8cbf26cd.png?resizew=124)
(1)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/896e293411e2fd0da215ff20781cb36a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/41104641f3e2260d00aeadf8fb8a078a.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1c823e54bf3a3a7f1916a4886eb6279.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/41104641f3e2260d00aeadf8fb8a078a.png)
您最近一年使用:0次
解答题-证明题
|
适中
(0.65)
名校
解题方法
【推荐2】如图,已知在三棱锥
中,
,点
分别为棱
的中点,且平面
平面
.
平面
;
(2)求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63397cda22cb1fad59cf966dfb588643.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cb96e0331eebe80ed1ff610faf531fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7789a500686c7a73770404ead6af0590.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cca04b2a2b61d62a809776670a60c09.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d077f6da8b2c00b152d4679aa2ed7f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/307807ee10071bafbe922eb18d2517d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22ce50ba5e349425274f05d46d120a74.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/764756fb1bdb6b86c1e24a8aed83936c.png)
您最近一年使用:0次
解答题-证明题
|
适中
(0.65)
【推荐1】如图,在四棱锥
中,
平面
,且
,
,
,且
,
.
![](https://img.xkw.com/dksih/QBM/2018/2/9/1878612782825472/1878832567599104/STEM/19b9791fb1e7475587e2c825d0278468.png?resizew=185)
(Ⅰ)求证:平面
平面
;
(Ⅱ)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c4cb73e9d976cbfe9c590044fa69dd5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/829f9180ddd9aa1a0ee0dc520f4e0b5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c71622531dfa894f21b2da123d020d24.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a98c8e36238ad90378e724466fcb6023.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4bd6a2b112facda441f4e34bf5c145fa.png)
![](https://img.xkw.com/dksih/QBM/2018/2/9/1878612782825472/1878832567599104/STEM/19b9791fb1e7475587e2c825d0278468.png?resizew=185)
(Ⅰ)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78a3fd5284e160896f07ce367645fd04.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e582d73b96ba649378379c3074d506d.png)
(Ⅱ)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e867e5c7ef4da37d8985ce82022060e.png)
您最近一年使用:0次
解答题-证明题
|
适中
(0.65)
名校
解题方法
【推荐2】如图1,平面四边形
中,
和
均为边长为
的等边三角形,现沿
将
折起,使
,如图2.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/20/c0a38a07-d8a3-4f41-a29c-380b73216e9c.png?resizew=291)
(1)求证:平面
平面
;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76981622e3684aca12435743b6a08a8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c025ee3317be1099b7bf03a11e37ed4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/38387ba1cadfd3dfc4dea4ca9f613cea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c025ee3317be1099b7bf03a11e37ed4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cc17568125c6449fb22759bac6d95c89.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/20/c0a38a07-d8a3-4f41-a29c-380b73216e9c.png?resizew=291)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78a3fd5284e160896f07ce367645fd04.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b33b7213d99a817bff19bcf740a0697c.png)
您最近一年使用:0次