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解题方法
1 . 如图甲,在直角三角形
中,已知
,
,
,D,E分别是
的中点.将
沿
折起,使点A到达点
的位置,且
,连接
,得到如图乙所示的四棱锥![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2792f6f1fde407c93201c0f3fad39d52.png)
,M为线段
上一点.
![](https://img.xkw.com/dksih/QBM/2021/12/27/2881711704768512/2883062489751552/STEM/fec3dcb7-0cff-40c0-b9e1-a756f6dfb4bb.png?resizew=286)
(1)证明:平面
平面
;
(2)过B,C,M三点的平面与线段A'E相交于点N,从下列三个条件中选择一个作为已知条件,求直线DN与平面A'BC所成角的正弦值.
①
;②直线
与
所成角的大小为
;③三棱锥
的体积是三棱锥
体积的![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c77a22740bd1ad5f5979e4579cb177d0.png)
注:如果选择多个条件分别解答,按第一个解答计分.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/080db3af81b29ed10144a1c2e2a4fb8a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e65a3e478bb87d094e3a0af30dd10ae8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54275b7e571660d0a9e0370fbfe5050b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7dec2ca6438c82b43f746057d8129885.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7c314398e26ffc7164b82946eeb4273.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4772895af07cae75fc85a48507952c9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea7b7e2f8b77c8a8518198511b458233.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2792f6f1fde407c93201c0f3fad39d52.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1333acc72211e3ddb9a0f8c726ce8a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a21897349d3d7c94419692106887153.png)
![](https://img.xkw.com/dksih/QBM/2021/12/27/2881711704768512/2883062489751552/STEM/fec3dcb7-0cff-40c0-b9e1-a756f6dfb4bb.png?resizew=286)
(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7789069cf57bd1059f5e0f9ac61d933b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1333acc72211e3ddb9a0f8c726ce8a5.png)
(2)过B,C,M三点的平面与线段A'E相交于点N,从下列三个条件中选择一个作为已知条件,求直线DN与平面A'BC所成角的正弦值.
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c7f8da1f66714eba7f2867a19d02479.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b46c607b3deac746c0ef3389ad8f65c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79a97bb4dcfab4ec7539bc783d563c49.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee48b4d6b9ee347b2ba6305f2fdc2bb0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f04aab7c8fe102e94d113cad242921a0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c77a22740bd1ad5f5979e4579cb177d0.png)
注:如果选择多个条件分别解答,按第一个解答计分.
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3卷引用:四川省成都市2021-2022学年高三第一次诊断性检测理科数学试题
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2 . 如图,已知正四棱锥
与正四面体
所有的棱长均为
.
![](https://img.xkw.com/dksih/QBM/2021/7/8/2759751319707648/2777760744325120/STEM/ede128cb-f7cd-45e0-b834-efbf130c4aef.png?resizew=477)
(1)若
为
的中点,证明:
平面
;
(2)把正四面体
与正四棱锥
全等的两个面重合,排成一个新的几何体,问该几何体由多少个面组成?并说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/faeb97acf19bd3b2c6c77c2814df4d2f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/858d5bfe390d0cb79cee200241240a31.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://img.xkw.com/dksih/QBM/2021/7/8/2759751319707648/2777760744325120/STEM/ede128cb-f7cd-45e0-b834-efbf130c4aef.png?resizew=477)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d4db9b82b67efe45a02fca32bfcf5dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca6d50356a01ae13936f1bd8efa94c98.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb304d905125170bebfada27e7ed8960.png)
(2)把正四面体
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/858d5bfe390d0cb79cee200241240a31.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/faeb97acf19bd3b2c6c77c2814df4d2f.png)
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3卷引用:四川省成都第七中学2021-2022学年高二上学期入学数学(理科)试题
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3 . 国家主席习近平指出:中国优秀传统文化有着丰富的哲学思想、人文精神、教化思想、道德理念等,可以为人们认识和改造世界提供有益启迪.我们要善于把弘扬优秀传统文化和发展现实文化有机统一起来,在继承中发展,在发展中继承.《九章算术》作为中国古代数学专著之一,在其“商功”篇内记载:“斜解立方,得两壍堵.斜解壍堵,其一为阳马,一为鳖臑”.刘徽注解为:“此术臑者,背节也,或曰半阳马,其形有似鳖肘,故以名云”.鳖臑,是我国古代数学对四个面均为直角三角形的四面体的统称.在四面体
中,
平面
.
![](https://img.xkw.com/dksih/QBM/2021/7/9/2760356260454400/2761304616468480/STEM/acdd4b31b8504295b1d47e95e3567ddf.png?resizew=455)
(1)如图1,若
、
、
分别是
、
、
三边的的中点,
在
上,且
,求证:
平面
;
(2)如图2,若
,垂足为
,且
,
,
,求直线
与平面
所成角的大小;
(3)如图2,若平面
平面
,求证:四面体
为鳖臑.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e9e1bf2cc650448488a19c6301125b31.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9cf468f5132e14ee1d8cc766808b11af.png)
![](https://img.xkw.com/dksih/QBM/2021/7/9/2760356260454400/2761304616468480/STEM/acdd4b31b8504295b1d47e95e3567ddf.png?resizew=455)
(1)如图1,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.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/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73465a1f9aa03481295bf6bd3c6903ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dec0d25fa88ea9f0b003b83b7e2fe88a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f28f9f503c0a023ed7e78e48123cc95.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
(2)如图2,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d900531973c546625694146fa1509ab9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/618c5704137191d21172232bdb26b4d8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68b40d0d2f3cdd8981bb792ad87efb42.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71807a35b3170fce28ee6edf4c00d083.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf4c26f3f4d96117f087400a0f32ece8.png)
(3)如图2,若平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1095b030f441de5fb223781b00f3dd9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aeb5255e2159617505e0c87d01437a57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e9e1bf2cc650448488a19c6301125b31.png)
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