如图,在三棱锥
中,
是边长为4的正三角形,
,
,
分别为
,
的中点,且
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/7/8ba697c3-09b7-426d-be73-52d0c2064a3a.png?resizew=162)
(1)证明:
平面ABC;
(2)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/41e5db1d2fd912f77923e4c120a7dc19.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55ca6072b3a2aac406a2b60bb7e01cde.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5bea27e2052fcaae1f3312f62bd90f86.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/7/8ba697c3-09b7-426d-be73-52d0c2064a3a.png?resizew=162)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d30637da200a07672ae231b4c5c09cd.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0262d3168bd3296cc63c4d78965cbb2c.png)
更新时间:2021-03-28 12:41:14
|
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解答题-证明题
|
较易
(0.85)
解题方法
【推荐1】如图,
是圆
的直径,
垂直圆
所在的平面,
是圆
上的点.
![](https://img.xkw.com/dksih/QBM/2021/8/22/2791483258232832/2795181474963456/STEM/7ec1c650-4713-44b7-9239-8f0e999b1dad.png?resizew=252)
(1)求证:
平面
;
(2)设
为
的中点,
为
的重心,求证:面
平面
.
![](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/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://img.xkw.com/dksih/QBM/2021/8/22/2791483258232832/2795181474963456/STEM/7ec1c650-4713-44b7-9239-8f0e999b1dad.png?resizew=252)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2ffc6952e988d04f22f0fb2f7f0ab7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0628681907ac8d7fdb94d8bc1b15feb9.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2bbf9680f74a9ac5d934304654ce2771.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b61d5745414c0452adb4852d377d8f4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
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【推荐2】如图,
中,
,ACDE是边长为6的正方形,平面
底面ABC.
求证:
平面EAB;
求几何体AEDCB的体积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b7a85dc7ffaf67456db861cb1ef95d7c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a3ff8f4eee27e5ead5ba9ffbe7f602e0.png)
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解答题-问答题
|
较易
(0.85)
解题方法
【推荐1】如图,在四棱锥
中,
平面ABCD,
,
,
,且直线PB与CD所成角的大小为
.
(1)求BC的长;
(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/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1134c8e3440abb6cd385af2c169037fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4adf90a8c2b29334cdc5aa5b554991f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/428f2a90ece9b364272c0dd365b84ab2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d88591679796c52024d11c4de641bdb.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/15/66c9991a-3ab5-4b3d-ad70-04195962c8c6.png?resizew=174)
(1)求BC的长;
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1ac2a2bb310b6d49725ebbe7581c3b6.png)
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【推荐2】如图,在三棱柱
中,平面
平面
,
.
;
(2)求二面角
的正弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42d3a82b8e587ee890467835bc4e854c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0671b4776e142e17a79af5b3f0378ef7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d16867cc0fe4d229ff757b6bc44dcac7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cf1cc9995c3846117daa8cf10aadf22.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3fd38f4fd6af2418573bcc7b67119be5.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb23540401925e0126a2f64304b78c73.png)
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名校
【推荐3】如图,四棱锥
,底面
是正方形,
,
,
,
分别是
,
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/2/e12eacc2-7139-40e0-a29b-0dddcb7de54f.png?resizew=174)
(1)求证
;
(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/298f423208408bf66383df4f8cbe5e28.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/069861e12b842ee7862ce91e870bc606.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/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/2/e12eacc2-7139-40e0-a29b-0dddcb7de54f.png?resizew=174)
(1)求证
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a0b29cc24e75be59cbaa5c60a4b4c6e.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/864689852707154e3a9be79f657f16d4.png)
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