如图,四棱锥
中,底面
是边长为 4的菱形,
,
,
为
中点.
![](https://img.xkw.com/dksih/QBM/2016/3/4/1572518713155584/1572518718963712/STEM/2d0a5c44c5294384ba697fd8c1b2494c.png?resizew=223)
(1)求证:
平面
;
(2)求证:平面![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65277734669566578cbb7d690bb200fb.png)
平面
;
(3)若
,求三棱锥
的体积.
![](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/f75cf0288e9b7c31a426aff6b91a5a8e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b86db010859f7a243badec02946a4e24.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://img.xkw.com/dksih/QBM/2016/3/4/1572518713155584/1572518718963712/STEM/2d0a5c44c5294384ba697fd8c1b2494c.png?resizew=223)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1b70cef0b79ca64acbb67dc667fc53b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65277734669566578cbb7d690bb200fb.png)
(2)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65277734669566578cbb7d690bb200fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1633988fd62a652de726ee92a917b52d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0628681907ac8d7fdb94d8bc1b15feb9.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8cb96e0331eebe80ed1ff610faf531fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/578fc8dd7d45fd2799f7d05ac89a2024.png)
更新时间:2016-12-04 03:20:26
|
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解答题-证明题
|
较难
(0.4)
【推荐1】折纸与数学有着千丝万缕的联系,吸引了人们的广泛兴趣.因
纸的长宽比
称为白银分割比例,故
纸有一个白银矩形的美称.现有一张如图1所示的
纸
,
.
分别为
的中点,将其按折痕
折起(如图2),使得
四点重合,重合后的点记为
,折得到一个如图3所示的三棱锥
.记
为
的中点,在
中,
为
边上的高.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/24/0860ba53-b73d-4fcb-a66a-00e9537790c1.png?resizew=633)
(1)求证:
平面
;
(2)若
分别是棱
上的动点,且
.当三棱锥
的体积最大时,求平面
与平面
所成锐二面角的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b553e2a281714677e29a5e97dd7d5a3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d76e86c1dcc191aa8d51b3a528a454d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b553e2a281714677e29a5e97dd7d5a3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b553e2a281714677e29a5e97dd7d5a3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aea384826175316e3c89f68abd8e2ee1.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d145eb8c957ce58cb3e863799fefc1dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4cff11306570d48789612d7f8b9ae4f.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c1b4458e5ec7a7e18f3fa1faad8fab08.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/24/0860ba53-b73d-4fcb-a66a-00e9537790c1.png?resizew=633)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/953fb6ab7a1e12ce9c2d7e546c9bc097.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4eb7e9ad5486cf1c5e506b20c5469e8.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7490886e2807c7b8a4fa57d99c4dc3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5415c235863bfba1008463d855d14bea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29819c98ebd087116d5e579f4f088fe8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fdc41036afa324c4382f9045838cd01.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3ddc76d96d6951ebfef3fe63892a1114.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/193b5b41994c2a4dfa5bb0bc984061cc.png)
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解答题-证明题
|
较难
(0.4)
名校
【推荐2】如图,在四棱锥
中,
平面![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c707f0202ec1aa233e1eeacc7a4587d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0fbc98fa18c1c08c88c95b15aee6d6bf.png)
,
为线段
上一点不在端点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/5/0b75dba1-b8be-435a-8e47-e736fde06d9b.png?resizew=193)
(1)当
为中点时,
,求证:
面![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a0cbbcc3d79bf999588882e7b1b4324.png)
(2)当
为
中点时,是否存在
,使得直线
与平面
所成角的正弦值为
,若存在求出M的坐标,若不存在,说明理由.
![](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/9c707f0202ec1aa233e1eeacc7a4587d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0fbc98fa18c1c08c88c95b15aee6d6bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/685f60234c313fba13f5d706372b788b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7789a500686c7a73770404ead6af0590.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62794ea73abc2a84aa0512c5b205eb12.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/5/0b75dba1-b8be-435a-8e47-e736fde06d9b.png?resizew=193)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4bb9d08376d152bf4deed8b7e266b7fc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/02438f0423acd0ff2dfa5ffb6abf143f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4a0cbbcc3d79bf999588882e7b1b4324.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7b7c83470489253394bd288d7c920df.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9868f77d5ab5073b6145f1c6d272122e.png)
您最近一年使用:0次
解答题-问答题
|
较难
(0.4)
名校
【推荐1】已知四棱锥
的底面
是直角梯形,
,
,
为
的中点,
.
![](https://img.xkw.com/dksih/QBM/2018/5/23/1951662548353024/1952731584282624/STEM/9625e534c20e443e94497dc8ecbe31fb.png?resizew=173)
(1)证明:平面
平面
;
(2)若
与平面
所成的角为
,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/34e0a957a55460c72673c0f2ee90dbb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/073cbc45075b24c4137cbc04c4ef9f80.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aaef9e92d148afff22761d5e027d3ee.png)
![](https://img.xkw.com/dksih/QBM/2018/5/23/1951662548353024/1952731584282624/STEM/9625e534c20e443e94497dc8ecbe31fb.png?resizew=173)
(1)证明:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f04c222223dae9ef27d4c132534d9848.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/596919118348e4fb08f03b713e5f9c9b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/af9955b5aebb73cd84447e8541f901ac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/caa431d661bf9f419e8ab713dd4a3c80.png)
您最近一年使用:0次
解答题-证明题
|
较难
(0.4)
名校
解题方法
【推荐2】长方形
中,
,
是
中点(图1).将
沿
折起,使得
(图2)在图2中:
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/21/0ceb27fa-6ff1-4cdc-a288-a844502a8b82.png?resizew=339)
(1)求证:平面
平面
;
(2)在线段
上是否存点
,使得二面角
的余弦值为
,说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35e9d1af332ceac3c412a17b86bc7054.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7f9fba8a4098c1a0515286eb8d616dc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/804c0e2a375b5f4ff1c420532968efc3.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/11/21/0ceb27fa-6ff1-4cdc-a288-a844502a8b82.png?resizew=339)
(1)求证:平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0bb5012f6c70a1e98d682b6d021fadd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0760712e3e2ea02b755b751e760d0c55.png)
(2)在线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a5266895d3c1fcb350a745bc779433b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dee14db57f0c762aad845cf5b4a243c0.png)
您最近一年使用:0次