已知
,
,
.
(1)求
值;
(2)求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3471cb48030b71f02172f5f512356789.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11dba4df4d2363ca61e2743b8c07e393.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ba4d36c998e1cca82a8e0d5c33e2b0c.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9381b769d58b82926d9daec0fee14345.png)
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8dc4c63a548b91061528aa11058de75.png)
更新时间:2020-02-15 22:25:13
|
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解答题-问答题
|
适中
(0.65)
名校
解题方法
【推荐1】已知矩形
中,
,
的中点为
,将
绕着
折起,折起后点
记作
点(不在平面
内),连接
、
得到几何体
,
为直角三角形.
(1)证明:平面
平面
;
(2)求平面
与平面
所成角的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/585288e61871608f6ff8f7e4a0beafbf.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/20a5e0a51c9e14fb246b0ba0b231c1e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e69d2b798744645af88a4fa411344a83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f9e5a462c0ca3b9e2c603750a3b433b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0629ce42392a7fe9be21d25c39c3e64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c0e8a78e361708ecbcc07d217308d1e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c025ee3317be1099b7bf03a11e37ed4.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/7/21/ea4fe6fa-06d8-45da-bf90-21ce3606b93f.png?resizew=159)
(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d24305d21268a9b67cf6a8daae6bbe4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f9e5a462c0ca3b9e2c603750a3b433b.png)
(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f747eb5b2d21c9de962cbfd4ec4bb7.png)
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解答题-问答题
|
适中
(0.65)
【推荐3】在锐角三角形ABC中,
,
,求
,
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15ee608882881caff2f1e223177424ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bdd7a233d545b5eeb082e81488c4667b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8e5d4f93699f8dcffb0e7840ca5597e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6402f1010e94be78552ed4c45548b1b8.png)
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解答题-证明题
|
适中
(0.65)
名校
【推荐1】(1)锐角三角形
中,
.
,求
的值.
(2)已知
,
,其中
,
.求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15ee608882881caff2f1e223177424ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80fafa5beb70c80533bb17b31fb5416f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6402f1010e94be78552ed4c45548b1b8.png)
(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/da951e45061c4a21b216e04fca76a99c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87bad4c3f9aba47bccdbcc961542c0b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea52ac55e2361a8ccc1664fd91abfb96.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6dffd51af6a5a4d5e2492d8555fa0c10.png)
您最近一年使用:0次
【推荐2】设
的内角
、
、
的对边分别为
、
、
,其中
,已知
.
(1)求角
的大小;
(2)在①
,②
,③
这三个条件中任选一个__________,若这样的三角形存在,求三角形的周长;若该三角形不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/071a7e733d466949ac935b4b8ee8d183.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/036b23c94e305faaa1283996edc5b30c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8a5950965950209521b0c6d5be3f23c.png)
(1)求角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
(2)在①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a72335ff513c24f55115bd073ab7c9a6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93373ae43b3be7a6e01557e62520a2ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85aa728b4dd424c067584a236c4d7e1f.png)
您最近一年使用:0次