如图,三棱柱
中,四边形
是矩形,
是
的中点,
,
,平面
平面
.
![](https://img.xkw.com/dksih/QBM/2020/1/30/2388408865710080/2389111566606336/STEM/6bc449ecb0304f03b8712db6579ff4c2.png?resizew=145)
(1)求证:
平面
;
(2)求锐二面角
的平面角的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76dce366399127d49c9a9e6ce3b81e4e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31e55e398e8520d8a36fb5a625a085b8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29bb8ab7c2b4e68bae55828bcf240d33.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7aab4339f6797832d4ef88c5d58709fa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ec2c25043792c34542464cbb6f955116.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://img.xkw.com/dksih/QBM/2020/1/30/2388408865710080/2389111566606336/STEM/6bc449ecb0304f03b8712db6579ff4c2.png?resizew=145)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a22d6b860f06fe23618b0d3de6768fa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e51817ee1ebf17c73ed21171bcfc5b5.png)
(2)求锐二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/382940a9e0b1a45d525e5f2460c015ea.png)
更新时间:2020-01-31 20:42:50
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【推荐1】某商品的包装纸如图1,其中菱形
的边长为3,且
,
,
,将包装纸各三角形沿菱形的边进行翻折后,点E,F,M,N汇聚为一点P,恰好形成如图2的四棱锥形的包裹.
![](https://img.xkw.com/dksih/QBM/2021/11/1/2841764115521536/2844888435130368/STEM/57547906-c9e6-45d6-acdb-400ac2b3ac5b.png?resizew=292)
(1)证明
底面
;
(2)设点T为BC上的点,且二面角
的正弦值为
,试求PC与平面PAT所成角的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e075468e7fb0bf30229aec01a7205977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5d28bead45d13aea39356bbae4b7b1a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c11cf3a79f306472abcd43f2c00bfe4.png)
![](https://img.xkw.com/dksih/QBM/2021/11/1/2841764115521536/2844888435130368/STEM/57547906-c9e6-45d6-acdb-400ac2b3ac5b.png?resizew=292)
(1)证明
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(2)设点T为BC上的点,且二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd013aa647d5d82d414644f08d5c4c6f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d172f55bc57ef5b5c2c1ad5b167440b2.png)
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【推荐2】如图,在直三棱柱
中,AB=BC,D、E分别为
的中点.
![](https://img.xkw.com/dksih/QBM/2018/4/17/1926138813710336/1930101661892608/STEM/206e91192eb14d9f968f5bbd35d7615e.png?resizew=124)
(1)证明:ED为异面直线BB1与AC1的公垂线段;
(2)设AB=1,
,求二面角A1—AD—C1的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0b66f50f883c7574306d2922e5e25e8c.png)
![](https://img.xkw.com/dksih/QBM/2018/4/17/1926138813710336/1930101661892608/STEM/206e91192eb14d9f968f5bbd35d7615e.png?resizew=124)
(1)证明:ED为异面直线BB1与AC1的公垂线段;
(2)设AB=1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5af052c9203aa2e8db5bddc1420a7ed2.png)
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解题方法
【推荐1】如图①,在正方形
中,E,F分别是边
的中点,将
沿
折起,使得
为正三角形,如图②所示.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/29/c7d17a2b-e009-4de3-8bb0-a2763b973037.png?resizew=221)
(1)证明:点A在平面
内的射影G在直线
上;
(2)求平面
与平面
夹角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5c4cd264c97c1f261229925cc5a6761.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/7ac451db3443cabb204f96c31fd4a02e.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/29/c7d17a2b-e009-4de3-8bb0-a2763b973037.png?resizew=221)
(1)证明:点A在平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fa7bbd7831e9ff4f8cffc8889d34f05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9a32bd7a1b78b5a0ec562c4025aea8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fa7bbd7831e9ff4f8cffc8889d34f05.png)
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【推荐2】如图,在四棱锥
中,四边形
是边长为2的正方形,平面
平面
,
,
与平面
所成的角为45°.
![](https://img.xkw.com/dksih/QBM/2020/12/30/2625301535260672/2628353819754496/STEM/18643bbc356340b79635e69a5f305aff.png?resizew=188)
(1)求证:平面
平面
;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78a3fd5284e160896f07ce367645fd04.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c383691e8d740830a865b12d66f7633.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
![](https://img.xkw.com/dksih/QBM/2020/12/30/2625301535260672/2628353819754496/STEM/18643bbc356340b79635e69a5f305aff.png?resizew=188)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/78a3fd5284e160896f07ce367645fd04.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e582d73b96ba649378379c3074d506d.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87aed767c861502aff771e6b0114746c.png)
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【推荐3】如图,P为圆锥的顶点,O为圆锥底面的圆心,AB为底面直径,四边形POBC是梯形,且
,
,
,D为圆O上一点.
(1)若点M在线段AD上,且
,求证:
∥平面CDB;
(2)当直线PD与平面PAB所成的角为30°时,求二面角
的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/061248f4e3932ad43c1abd52ada56a4a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23b93b8e3f2196f571782a283f2e10ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5d3530ee12bd68b53970b83f28985b31.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/9/b1f43728-6dfd-4cfb-9393-8828e4fb8ffa.png?resizew=168)
(1)若点M在线段AD上,且
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/963f0cda34e54f15725cee9448a4537e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/892909e49156f7dcc0650fcd65243877.png)
(2)当直线PD与平面PAB所成的角为30°时,求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad6a0cee8226e82cc57916e10d533369.png)
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