过
所在平面
外一点
作
,垂足为
,连接
,给出下面四种说法:
①若
,则点
是
的外心;
②若点
到
三边所在直线的距离都相等,则点
是
的内心;
③若
,
,
,则点
是
的垂心;
④若
与平面
所成的角都相等,则点
是
的外心.
其中所有正确说法的序号是_____ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59169f91ebc758ba6e73fc99fcfaab15.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19bb1063e139610045f3bca5ca0b2766.png)
①若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/30fc65a72853bd8ac1ad0828270d3baf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
②若点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](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/15c0dbe3c080c4c4636c64803e5c1f76.png)
③若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83640592853a53872d7af69c0cffc1bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8a916d31a199e250556fb7478d9f57f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/036de574712cad14bddadf6653c7e714.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
④若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19bb1063e139610045f3bca5ca0b2766.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
其中所有正确说法的序号是
更新时间:2020-02-12 11:17:44
|
相似题推荐
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【推荐1】设
是空间不同的直线或平面,对下面四种情形,使“
且
”为真命题的是___________ (填序号).
①
是直线; ②
是直线,
是平面;
③
是直线,
是平面; ④
是平面.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a14c388e1e2e5a2ff1ccf6caffbee0d.png)
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①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a14c388e1e2e5a2ff1ccf6caffbee0d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e81e59019989b7dc2fb59b037ef6e010.png)
③
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e81e59019989b7dc2fb59b037ef6e010.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0fffbec1fe851795dfdd448bf0d165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a14c388e1e2e5a2ff1ccf6caffbee0d.png)
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【推荐2】下列命题中,所有正确的命题的序号是________
①一条直线和两条直线平行线中的一条垂直,则它也和另一条垂直;
②空间四点A、B、C、D,若直线AB和直线CD是异面直线,那么直线AC和直线BD也是异面直线;
③空间四点若不在同一个平面内,则其中任意三点不在同一条直线上;
④若一条直线l与平面
内的两条直线垂直,则
.
①一条直线和两条直线平行线中的一条垂直,则它也和另一条垂直;
②空间四点A、B、C、D,若直线AB和直线CD是异面直线,那么直线AC和直线BD也是异面直线;
③空间四点若不在同一个平面内,则其中任意三点不在同一条直线上;
④若一条直线l与平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e380108ba2cf04e68a5a9393d2b921c.png)
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名校
【推荐1】如图,平面
平面
,
,
,AB与两平面
、
所成的角分别为45°和30°,过A、B分别作两平面交线的垂线,垂足为
、
,若AB=12,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4ae2d8122aecb3f04c7b1160d3a67ad.png)
______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fa807136194c18d3ac58902c67f9333.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb0b6de90bb936cdb09629123100145d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16acea101c98a280a70c2fa0b2c04dd7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7c314398e26ffc7164b82946eeb4273.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3953cec61ac602ce5eb59b7912352179.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4ae2d8122aecb3f04c7b1160d3a67ad.png)
![](https://img.xkw.com/dksih/QBM/2022/4/21/2962988854042624/2964182991642624/STEM/c02a6da7-abff-4b1a-b637-6e3d79e2f248.png?resizew=211)
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解题方法
【推荐2】如果直线AB与平面
相交于B,且与
内过点B的三条直线BC,BD,BE所成的角相同,则直线AB与CD所成的角=_________ .
![](https://img.xkw.com/dksih/QBM/2015/4/30/1572089555517440/1572089561366528/STEM/75512247af6e4940b691a1abd1e5b66e.png?resizew=16)
![](https://img.xkw.com/dksih/QBM/2015/4/30/1572089555517440/1572089561366528/STEM/75512247af6e4940b691a1abd1e5b66e.png?resizew=16)
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解题方法
【推荐1】如图,正方体
的棱长为1,点P是线段
上的动点,给出以下四个结论:
①
;
②三棱锥
体积为定值;
③当
时,过P,D,C三点的平面与正方体表面形成的交线长度之和为3;
④若Q是对角线
上一点,则PQ+QC长度的最小值为
.
其中正确的序号是______ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83c09eec4e14a861af83d7828797d176.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8321030a00628262634b3857e38e4c55.png)
②三棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e76553e35a0b48413eda37b26e665870.png)
③当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70566cd51557461fe19e8a2e03f7b81f.png)
④若Q是对角线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24bb49fdc6b6bbb2449fdf8a0de769d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d599cb4a589f90b0205f24c2e1fa021e.png)
其中正确的序号是
![](https://img.xkw.com/dksih/QBM/2022/7/13/3021642901618688/3024649948020736/STEM/de0a677ea24d4d928f11d745a2cd2856.png?resizew=225)
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解题方法
【推荐2】
、
是正三角形
的边
、
的中点,沿
把正三角形折成
的二面角(如图),则
的正切值为_____________
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d5bca00fa20e6e80480b9d06d2e52ee.png)
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【推荐3】在正三棱锥
中,M、N分别是校SA、AB的中点,且
,若侧棱
,则正三棱锥
外接球的体积是______ .
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8300bca7b13f8487061c5d6d2e82802.png)
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