名校
1 . 如图所示,四棱台
,底面
为一个菱形,且
. 底面与顶面的对角线交点分别为
,
.
,
,
与底面夹角余弦值为
.![](https://staticzujuan.xkw.com/quesimg/Upload/formula/192f4f9446c954a291f779d963f90257.png)
平面
;
(2)现将顶面绕
旋转
角,旋转方向为自上而下看的逆时针方向. 此时使得底面与
的夹角正弦值为
,此时求
的值(
);
(3)求旋转后
与
的夹角余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d07c321ebb740613ff53c1d6e496ee85.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23f919bd3dde10dbbc076f7ec5149699.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c2a61472439de1ba85cfe33840b775f2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d76ce5fcc2291de26b44b4b082df5cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb34d99a48c5d1d8f21af99c1b70ea49.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/192f4f9446c954a291f779d963f90257.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1633988fd62a652de726ee92a917b52d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(2)现将顶面绕
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/192f4f9446c954a291f779d963f90257.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f2eb89294b31ffdd2680b4361e8994d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2236f820e9625bcc1e81f101e9ab7713.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4967af4c76d238fea5695537dfc9e91e.png)
(3)求旋转后
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2777840758e70e7dbbc18cef8f3d6d2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0a851907ada2ac2c3c4880a6736d28a.png)
您最近一年使用:0次
2 . 如图,已知四边形
是直角梯形,
,
平面
是
的中点,E是
的中点,
的面积为
,四棱锥
的体积为
.
平面
;
(2)若P是线段
上一动点,当二面角
的大小为
时,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34ddc0e6db5f4acd18f4765e05d44bc8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21ec59cea09acc43a8178af846693cdf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/06b39b0cfa27b633312db83601cf0359.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6830ebecddbd9759be626289c408e4f3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/adbd3e8cf8325999cde03adf845d3dd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e5ba482836565abad208665cf7b9972.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6093eebca8f3ff82ce9298feb197e955.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca5dd496ee0c1170ef6dcc48266ee444.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6895da13331cb525f5850d7b7a02a847.png)
(2)若P是线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b74a85c6a0b3e431dc184d58f957090a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c02b54dc6b3e1bb6544f47d4c8743fcf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/297cc0f9553ef0c5b537c5581eee934c.png)
您最近一年使用:0次
名校
解题方法
3 . 在菱形
中,已知
,
.
是对角线
上一点,沿
把菱形折成二面角
,将折成二面角后的
点记作
,设
,点
在平面
上的射影记为
.
(1)当
是
的中点时,如图1,求证
平面
;
(2)当
落在菱形的边
上时,如图2,求二面角
的取值范围;
(3)设折痕
与菱形的边
交于点
,求四棱锥
体积的最大值(说明:可以用到必修一探究实践活动中得到的不等式![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d936ea1443a8c881633d5e04fdd3434.png)
).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7e918b70b02a73685e3c536c7f380e2c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcd0ced286a0fbc7e4862f8147264277.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8efa92fbb689ce6f9ab3384918f48774.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/3160d33de228937b8a691519fced22e7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca67a5b8f69507c8b80379e86f90a8ce.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73465a1f9aa03481295bf6bd3c6903ac.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/7/15/926446e4-566c-43a8-8e7c-da6d5f318095.png?resizew=342)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/662698361c6b3ddaf0c28a3c87be53e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0bf12905647aeeded72bbca21a63f319.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73465a1f9aa03481295bf6bd3c6903ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8efa92fbb689ce6f9ab3384918f48774.png)
(3)设折痕
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee724bdc07aa2bacb42d4779585a2a12.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d936ea1443a8c881633d5e04fdd3434.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d3ac744d01bdb607d6c2ffd7ef64a24.png)
您最近一年使用:0次
解题方法
4 . 如图1,在边长为4的菱形
中,
,
,
分别为
,
的中点,将
沿
折起到
的位置,得到如图2所示的三棱锥
.
;
(2)
为线段
上一个动点(
不与端点重合),设二面角
的大小为
,三棱锥
与三棱锥
的体积之和为
,求
的最大值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/284e282bb1d9fbf8634b3506ee5358ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ac451db3443cabb204f96c31fd4a02e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1a33d27a9c655d01f606e9bce02b0a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aedb55703d202771dd11987cf4f30bf6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/432129b84db4beea3395281639c6684e.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a6f4e64c96f4c48b158c7f918243fbd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f5d90f940f5693b22ddf2e7c761887d8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d7b329612a9159b0b2dce46120b409e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be54e84508decfcce6d2fcbe6c8c1a92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be54e84508decfcce6d2fcbe6c8c1a92.png)
您最近一年使用:0次
2023-07-11更新
|
462次组卷
|
2卷引用:山东省泰安市2022-2023学年高一下学期期末数学试题
2023·江西·二模
解题方法
5 . 正四棱锥
中,
,E为
中点,
,平面
平面
,平面
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/4/14/c52111ed-34c7-466f-ac0c-965dad82f80b.png?resizew=217)
(1)证明:当平面
平面
时,
平面![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f571a1aac46c6d0cf440c0ec2846bf9.png)
(2)当
时,T为
表面上一动点(包括顶点),是否存在正数m,使得有且仅有5个点T满足
,若存在,求m的值,若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f83a04565a8ebaa111894b724b0ba266.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/802645a50da02b13401938ab49c8ffab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25239a0102c88b1d9a16387cacc5842b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25cf5e1e2d2b61e7d9b488faf4284165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f954bc0713b5cf9526f9d352408dec64.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/4/14/c52111ed-34c7-466f-ac0c-965dad82f80b.png?resizew=217)
(1)证明:当平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5394d00a80a5900d7fd7d9961868bd22.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f571a1aac46c6d0cf440c0ec2846bf9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9df740160690029ac1e730c85f20347.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f571a1aac46c6d0cf440c0ec2846bf9.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8bbd9d74f6ddcfcf14c6b112256b1539.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15a37cf476f0ae3c25fd1932ca42022a.png)
您最近一年使用:0次
2023-04-10更新
|
1101次组卷
|
6卷引用:江西省名校协作体联盟2023届高三第二次联考模拟考试数学(理)试题
(已下线)江西省名校协作体联盟2023届高三第二次联考模拟考试数学(理)试题(已下线)重难点突破06 立体几何解答题最全归纳总结(九大题型)-3(已下线)第七章 综合测试B(提升卷)辽宁省2023-2024高二上学期期末考试阶段练习数学试题(已下线)专题04用空间向量研究直线、平面的位置关系(4个知识点6种题型2个易错点)(2)(已下线)3.4.1 判断空间直线、平面的位置关系(六大题型)(分层练习)-2023-2024学年高二数学同步精品课堂(沪教版2020选择性必修第一册)
名校
6 . 马戏团的表演场地是一个圆锥形棚,如图,
为棚顶,
是棚底地面的中心,
为棚底直径,
,
是棚底的内接正三角形,中间的支柱
米,从支柱上的
点向棚底周围拉了4根绳子
供动物攀爬表演,有一个节目表演的是猴子从
点沿着绳子
爬到
点,再沿着
爬到棚顶,然后从棚顶跳到
中的某一根绳子上.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/10/cf507ce4-ee84-41cc-84f5-4fe0841b5f99.png?resizew=176)
(1)当
点取在距离
点
米处时,证明拉绳
所在直线和平面
垂直;
(2)经验表明当拉绳
所在直线和平面
所成角的正弦值最大时,节目的观赏性最佳,问此时应该把
点取在什么位置.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e30e50e094cd2849e38859b36aad0b0c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/22538f4c49c5a0f1b1cf59773c218bd1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68d3c54b33e6ec883393f6630000446d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc5adb5eb60ae4435a12d93854066298.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0629ce42392a7fe9be21d25c39c3e64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92c7267e5313b9b00ef22c94a479fc34.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/10/cf507ce4-ee84-41cc-84f5-4fe0841b5f99.png?resizew=176)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ed0325097927b92a6458bfbb0667b81.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
(2)经验表明当拉绳
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc5adb5eb60ae4435a12d93854066298.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
您最近一年使用:0次
2023-03-09更新
|
867次组卷
|
2卷引用:安徽省黄山市2022-2023学年高二上学期期末数学试题
名校
7 . 如图,
是半球的直径,
为球心,
依次是半圆
上的两个三等分点,
是半球面上一点,且
,
![](https://img.xkw.com/dksih/QBM/2022/6/2/2992657885069312/2994303654756352/STEM/a8454b57-25b9-4515-8ac4-e5e4472e5be3.png?resizew=249)
(1)证明:平面
平面
;
(2)若点
在底面圆内的射影恰在
上,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a6c6eff038537d5fdae6e9741e2bd9dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16d65cecaf8a3dc2953f4109c75a981e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c16bb6dfa23ed5b89e42c95ce0590eae.png)
![](https://img.xkw.com/dksih/QBM/2022/6/2/2992657885069312/2994303654756352/STEM/a8454b57-25b9-4515-8ac4-e5e4472e5be3.png?resizew=249)
(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d24305d21268a9b67cf6a8daae6bbe4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb6b79de40c8517ab2650999401d7c3c.png)
(2)若点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e69d2b798744645af88a4fa411344a83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f42a997b72568fa71bd29bedd8be6f1.png)
您最近一年使用:0次
2022-06-04更新
|
3379次组卷
|
6卷引用:湖南师范大学附属中学2020-2021学年高一下学期期末数学试题
湖南师范大学附属中学2020-2021学年高一下学期期末数学试题(已下线)第02讲 玩转立体几何中的角度、体积、距离问题-【暑假自学课】2022年新高二数学暑假精品课(苏教版2019选择性必修第一册)湖北省武汉市新高考联合体2021-2022学年高一下学期期末数学试题安徽省合肥六校联盟2022-2023学年高一下学期期末联考数学试卷(已下线)第8章立体几何初步(基础、典型、易错、压轴)分类专项训练专题12空间中直线、平面的平行与垂直关系(解答题)
名校
8 . 已知△ABC是边长为6的等边三角形,点M,N分别是边AB,AC的三等分点,且
,
,沿MN将△AMN折起到
的位置,使
.
![](https://img.xkw.com/dksih/QBM/2022/3/21/2941122016854016/2941973344141312/STEM/2e8e1f2861954c9687b97882d744e8d7.png?resizew=424)
(1)求证:
平面MBCN;
(2)在线段BC上是否存在点D,使平面
与平面
所成锐二面角的余弦值为
?若存在,设
,求
的值;若不存在,说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba486b7a12ec874644dc5fea93a56916.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3a45b6f1348711bc6eabd87982c3756.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8e7040c2fd8a163d71e35805775feb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55d938067915b0d59f491b4c8ee7a982.png)
![](https://img.xkw.com/dksih/QBM/2022/3/21/2941122016854016/2941973344141312/STEM/2e8e1f2861954c9687b97882d744e8d7.png?resizew=424)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8eedf1e774ce129d9a09f02ca1920052.png)
(2)在线段BC上是否存在点D,使平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4459d0d7b4c2e9e8106fe5b4520277e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34c932cfbb9fb63159a176a8f45489a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c4e108d5c61e85e0741ec2c484fc5768.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8a2f0857ee6d2e3e5341bcc916f2e067.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
您最近一年使用:0次
2022-03-22更新
|
3713次组卷
|
7卷引用:河南省洛阳市2021-2022学年高三第二次统一考试理科数学试题
9 . 已知梯形
,现将梯形沿对角线
向上折叠,连接
,问:
![](https://img.xkw.com/dksih/QBM/2022/5/24/2986381346414592/2986469922070528/STEM/3206762a-48bc-4b44-ba5a-031fa02e6e8a.png?resizew=185)
(1)若折叠前
不垂直于
,则在折叠过程中是否能使
?请给出证明;
(2)若梯形
为等腰梯形,
,折叠前
,当折叠至面
垂直于面
时,二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fafac61dc0ff84d57596341d673a5703.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://img.xkw.com/dksih/QBM/2022/5/24/2986381346414592/2986469922070528/STEM/3206762a-48bc-4b44-ba5a-031fa02e6e8a.png?resizew=185)
(1)若折叠前
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70734a8e672376bb0bd1522e229f86a2.png)
(2)若梯形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70fcd24996744442421425824bd17fb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cfc1f76257275ab4b04f9bc913535670.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8d78fc7fcb2762de28dcef8aa3aa0e49.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f1854ba6cc92481d7a616bd2788a47e.png)
您最近一年使用:0次
名校
解题方法
10 . 为了求一个棱长为
的正四面体的体积,某同学设计如下解法.
解:构造一个棱长为1的正方体,如图1:则四面体
为棱长是
的正四面体,且有
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/16/6db5d8bf-a942-4eb1-b74e-0d41be5b6734.png?resizew=583)
(1)类似此解法,如图2,一个相对棱长都相等的四面体,其三组棱长分别为
,
,
,求此四面体的体积;
(2)对棱分别相等的四面体
中,
,
,
.求证:这个四面体的四个面都是锐角三角形;
(3)有4条长为2的线段和2条长为
的线段,用这6条线段作为棱且长度为
的线段不相邻,构成一个三棱锥,问
为何值时,构成三棱锥体积最大,最大值为多少?
[参考公式:三元均值不等式
及变形
,当且仅当
时取得等号]
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
解:构造一个棱长为1的正方体,如图1:则四面体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68ac02c2f91cadb1e328bc6ab9b9c491.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf298f00799cbf34b4db26f5f63af92f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6f878ffcff2ca25a434cbeea7d5c841.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/16/6db5d8bf-a942-4eb1-b74e-0d41be5b6734.png?resizew=583)
(1)类似此解法,如图2,一个相对棱长都相等的四面体,其三组棱长分别为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2967337e3fcb228dded64ab0c41a17e0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/50690dab38f4512eb72e18b7f86cf6f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4056761b8f826eeb6ad8c9a151d3c9c.png)
(2)对棱分别相等的四面体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c220eadc312101e2fb89dfe920f7b30d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7de966c316db1013defc56372fcf814e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8d2530e7023b2345c651e8f53629ff1.png)
(3)有4条长为2的线段和2条长为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
[参考公式:三元均值不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1ffb6b373d2e672bb2afc8de547861a2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4849ff71159df2bb9099b26065d81e1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/44acc0ee22dc4b7750e8be825e7c1355.png)
您最近一年使用:0次
2021-07-15更新
|
814次组卷
|
2卷引用:重庆市西南大学附属中学2020-2021学年高一下学期期末数学试题