如图①,在等腰
中,点
是底边
的中点,将
沿
折至
的位置.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/3/fbb6fb18-33ee-48dd-ac7f-7d0deff57135.png?resizew=174)
(1)求证:
平面
.
(2)若三棱锥
的三视图为图②所示的三个直角三角形,求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e195f36d43128197ea62c7f53ed57197.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2c3d2cba96f6f03520c0b3f6e4da03e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fded87a08e621a0aa62659e26232f85c.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/3/fbb6fb18-33ee-48dd-ac7f-7d0deff57135.png?resizew=174)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ce03b310edce42191f9fa75a1c909ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/739c629772c553e9a2329d5d71173736.png)
(2)若三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32c9a742c1e218d1fcdb92bce78123e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d3bceb0faeccb4766590b1da63f38a6.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/3/b3175e44-7823-4a0c-adc1-8d2d163e5261.png?resizew=289)
更新时间:2020-12-11 10:29:36
|
相似题推荐
解答题-证明题
|
较易
(0.85)
解题方法
【推荐1】如图,在四棱锥
中,已知
,
.证明:
平面
;
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21b69c41147a67cb486426ee88bd41ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7671472f1a86a828f71e441e431b70d6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42789f54f6d3e1d508837711c6a873b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eeebdf3d00c146a1b4d220909d7573c1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/828fcf6ed16b5dae1b572d471f5ed7a7.png)
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解答题-问答题
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(0.85)
解题方法
【推荐2】如图,四棱锥
的底面为直角梯形,
,
底面
,
,设平面
与平面
的交线为
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/27/8b6f49cb-c30e-4cc4-ba85-5741ea5d43e1.png?resizew=193)
(1)证明:
;
(2)证明:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
平面
;
(3)求点
到平面
的距离.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0585b6c0f156eecf9662b9846d4eb693.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/666c7e13a7999bd5970c1e478a665935.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c45fbffb9e2c7fa7c5006cde8da0cabe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5a915ebf5347aa0762ae3b9d205745e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/852aabd89edffc1b94344ff3f1f31ccd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/1/27/8b6f49cb-c30e-4cc4-ba85-5741ea5d43e1.png?resizew=193)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/207de39505bb8357599d8bf03b03cd9d.png)
(2)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1633988fd62a652de726ee92a917b52d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1e582d73b96ba649378379c3074d506d.png)
(3)求点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f747eb5b2d21c9de962cbfd4ec4bb7.png)
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解答题-问答题
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较易
(0.85)
【推荐1】如图,四棱锥
中,
底面ABCD,底面ABCD为菱形,且有
,
,
,E为PC中点.
平面BED;
(2)求二面角
的平面角的正弦值.
![](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/ced06b71073e1bb777f326f06016ce17.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/364d6c88726d8c3bb8ed297057332bac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e075468e7fb0bf30229aec01a7205977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/373f735f0f04d11f1951eaef1bb78b6a.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3e9d395e5501c87fec93dee44d24027.png)
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解答题-问答题
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较易
(0.85)
解题方法
【推荐2】已知正三棱柱底面边长为
,
是
上一点,
是以
为直角顶点的等腰直角三角形,
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/28/1526c21f-7aa1-4e05-8f9c-0ffc31aa6422.png?resizew=139)
(1)证明:
是
的中点;
(2)求二面角
的大小.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35361e76a7c85d1886728c8d0200b234.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c21f920814c1c5e76d3f3b72bd22934.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/28/1526c21f-7aa1-4e05-8f9c-0ffc31aa6422.png?resizew=139)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
(2)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7abc9839172e487277e8105ad4cd4b2.png)
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