在正方体
中,棱长为3,
是上底面
的一个动点.
(1)求三棱锥
的体积;
(2)当
是上底面
的中心时,求
与平面ABCD所成角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23f919bd3dde10dbbc076f7ec5149699.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/632f2bf1cd0435041fa04b01901d1c8c.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/23/306aaa3a-598c-4287-bb3f-de2491c5f218.png?resizew=160)
(1)求三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9308baeac7dc6f0962842e9efdc7f01c.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23f919bd3dde10dbbc076f7ec5149699.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/632f2bf1cd0435041fa04b01901d1c8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cee51552e3c12bc27cf8ab1777bf191.png)
更新时间:2023-06-22 23:08:47
|
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解答题-问答题
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适中
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【推荐1】如图所示,圆锥
的底面圆半径
,其侧面展开图是一个圆心角为
的扇形.
(1)求此圆锥的表面积;
(2)求此圆锥的体积.
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(1)求此圆锥的表面积;
(2)求此圆锥的体积.
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解答题-证明题
|
适中
(0.65)
名校
【推荐2】如图,在边长为
的正方形
中,点
,
分别为
,
的中点,将
折到
的位置.
![](https://img.xkw.com/dksih/QBM/2018/6/9/1963753912713216/1967890354503680/STEM/e83e3f86266a4edab28d8c9e4ebfb498.png?resizew=183)
(1)求证:
;
(2)若
,求五棱锥
的体积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8860d9787671b53b1ab68b3d526f5ca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61ba6f4177822927b5875b92cd5f2038.png)
![](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/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3634979dfcebf857b20874dd320d80b3.png)
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![](https://img.xkw.com/dksih/QBM/2018/6/9/1963753912713216/1967890354503680/STEM/e83e3f86266a4edab28d8c9e4ebfb498.png?resizew=183)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b30987c1ff8b2cc69bb6ad6c41bde18b.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/89b336e518ac4ff04c6c26e4b8a15844.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be89b9d1709d7974a108142c5fa2ccec.png)
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解答题-证明题
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适中
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【推荐1】如图,在四棱锥
中,底面
是菱形,
与
交于点
,
为线段
上的一点.
(1)证明:
平面
;
(2)当
与平面
所成角的正弦值最大时,求平面
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夹角的余弦值.
![](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/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b28e5765b200251b11d9327f5c593826.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eec666fc6d06ae552f2cae8d9fb32a2f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/23/e595a651-9d4c-4358-baae-9725d8170868.png?resizew=208)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ccd4fd4b7a4d6b8ca0c5827c055a9ce7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f571a1aac46c6d0cf440c0ec2846bf9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb304d905125170bebfada27e7ed8960.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
您最近一年使用:0次
解答题-证明题
|
适中
(0.65)
名校
解题方法
【推荐2】如图,在正三棱柱
中,
是
的中点,
是线段
上的动点,且
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/20/5ba9f6a1-cd82-417e-9c4e-c99b879a70dc.png?resizew=123)
(1)若
,求证:
;
(2)求二面角
的余弦值;
(3)若直线
与平面
所成角的大小为
,求
的最大值
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ede6a60cad0e0b58e1549fda6e085719.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/958217185cddb12466c9760248a4ca01.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b094e639c2b31dc54b1b3e6456e77843.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc65c549059934e69355d8ecc245da57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7895c919da3819abea641a35524afcdf.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/20/5ba9f6a1-cd82-417e-9c4e-c99b879a70dc.png?resizew=123)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8da022b26812ea653c7ed00cb1fb448.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c17067fa0e18231e358545529dbee69.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3f566da2725ef9999fccac9e27fb4ea.png)
(3)若直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aa29fe6cd9eb51c184f6299d437375cb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68ecff583dd5f216b28e0df718943ebc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4891e5861897266806a8c113be5e8ab9.png)
您最近一年使用:0次