1 . 如图,已知四边形
和
均为直角梯形,
,
且
,平面
平面
,
.
![](https://img.xkw.com/dksih/QBM/2017/1/19/1619466238443520/1619466239090688/STEM/f2541006f3b4496786f409f1c2468620.png)
(1)求证:
平面
;
(2)求平面
和平面
所成锐二面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/693cd6179b2a92f03153ce12a0e86b95.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34e0a957a55460c72673c0f2ee90dbb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cc3c947dc4deaf4eb5266772e43bee0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1057fba69b1554ceff580f73dbb28ff3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cf9a6db3571fa57bfa2d5e4d44c51b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/693cd6179b2a92f03153ce12a0e86b95.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/502fda7d60b3aa884b23094fac16ab63.png)
![](https://img.xkw.com/dksih/QBM/2017/1/19/1619466238443520/1619466239090688/STEM/f2541006f3b4496786f409f1c2468620.png)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e2fef2c0e49ecae8688ca60802310e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34be4e71cabf458f17a6cd7f24bc70af.png)
(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34be4e71cabf458f17a6cd7f24bc70af.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9a32bd7a1b78b5a0ec562c4025aea8c.png)
您最近一年使用:0次
2 . 如图,在四棱锥
中,底面
为直角梯形,
,
底面
,
,
为
的中点,
为棱
的中点.
![](https://img.xkw.com/dksih/QBM/2016/9/8/1573007093145600/1573007099224064/STEM/d180af331854481bba52a4ea298e7db0.png)
(1)证明:
平面
;
(2)已知
,求点
到平面
的距离.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6153163fecdf3f410411048428ccaef5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/083201b6b527a852ff51831bd71c99cc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e458f4503e211b542f6f30c8a34eaca5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f57cdaf395942435e770920e0cf62605.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://img.xkw.com/dksih/QBM/2016/9/8/1573007093145600/1573007099224064/STEM/d180af331854481bba52a4ea298e7db0.png)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df22ab3b1b32ff5e07407c133ed1bdcb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c233190f9339e777fe26c7b690541baf.png)
(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e159921cdcf0e3bb64ddc32015e1a361.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c233190f9339e777fe26c7b690541baf.png)
您最近一年使用:0次