如图,四边形ABCD为矩形,四边形ADEF为梯形,AD//FE,∠AFE=60º,且平面ABCD⊥平面ADEF,AF=FE=AB=
=2,点G为AC的中点.
![](https://img.xkw.com/dksih/QBM/2015/3/18/1572018274148352/1572018279931904/STEM/64e5bba7e4c24f2eb1c38239a8454a23.png)
(1)求证:EG//平面ABF;
(2)求三棱锥B-AEG的体积;
(3)试判断平面BAE与平面DCE是否垂直?若垂直,请证明;若不垂直,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a4cb1a4c5afb590c7c17de14d15651e1.png)
![](https://img.xkw.com/dksih/QBM/2015/3/18/1572018274148352/1572018279931904/STEM/64e5bba7e4c24f2eb1c38239a8454a23.png)
(1)求证:EG//平面ABF;
(2)求三棱锥B-AEG的体积;
(3)试判断平面BAE与平面DCE是否垂直?若垂直,请证明;若不垂直,请说明理由.
更新时间:2016-12-03 10:22:17
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【推荐1】如图,棱长为2的正方体
中,E、F分别是棱AB,AD的中点,G为棱
上的动点.
(1)是否存在一点G,使得
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(2)若直线EG与平面
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(3)求三棱锥
的外接球半径的最小值.
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(1)是否存在一点G,使得
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(2)若直线EG与平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7b54387f870ae37f7951b253665d64f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be6a6301878fed2a01413020b27310a5.png)
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(3)求三棱锥
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【推荐2】如图,在四棱锥
中,底面
是边长为2的菱形,
,
是正三角形,
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的中点,点
为棱
上的动点.
平面
;
(2)若平面
平面
.
①当点
恰为
中点时,求异面直线
与
所成角的余弦值;
②在平面
内确定一点
,使
的值最小,并求此时
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(2)若平面
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①当点
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/274cf35acb4a1748d15c39d15a9bea7b.png)
②在平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/64eb31601464364be2baf4aa87404bcd.png)
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【推荐1】如图,
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(2)当三棱锥
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(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9a32bd7a1b78b5a0ec562c4025aea8c.png)
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【推荐3】如图,某地质队自水平地面A,B,C三处垂直向地下钻探,自A点向下钻到A1处发现矿藏,再继续下钻到A2处后下面已无矿,从而得到在A处正下方的矿层厚度为A1A2=d1.同样可得在B,C处正下方的矿层厚度分别为B1B2=d2,C1C2=d3,且d1<d2<d3.过AB,AC的中点M,N且与直线AA2平行的平面截多面体A1B1C1﹣A2B2C2所得的截面DEFG为该多面体的一个中截面,其面积记为S中.
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(2)在△ABC中,记BC=a,BC边上的高为h,面积为S.在估测三角形ABC区域内正下方的矿藏储量(即多面体A1B1C1﹣A2B2C2的体积V)时,可用近似公式V估=S中﹣h来估算.已知V=
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