解题方法
1 . “费马点”是由十七世纪法国数学家费马提出并征解的一个问题,该问题是:“在一个三角形内求作一点,使其与此三角形的三个顶点的距离之和最小”.如图1,三个内角都小于
的
内部有一点
,连接
,求
的最小值.我们称三角形内到三角形三个顶点距离之和最小的点为费马点.要解决这个问题,首先应想办法将这三条端点重合于一点的线段分离,然后再将它们连接成一条折线,并让折线的两个端点为定点,这样依据“两点之间,线段最短”,就可求出这三条线段和的最小值.某数学研究小组先后尝试了翻折、旋转、平移的方法,发现通过旋转可以解决这个问题,具体的做法如图2,将
绕点
顺时针旋转
,得到
,连接
,则
的长即为所求,此时与三个顶点连线恰好三等分费马点
的周角.同时小组成员研究教材发现:已知对任意平面向量
,把
绕其起点沿逆时针方向旋转
角得到向量
.
,把点
绕点
沿顺时针方向旋转
后得到点
,求点
的坐标;
(2)在
中,
,借助研究成果,直接写出
的最小值;
(3)已知点
,求
的费马点
的坐标.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/231b861d6d1f1d0b9f52b041cb40eb62.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
(2)在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b11bf8ee11289d13cf5dd0ea9505e699.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7ed53a398b1d6b7b4abbb43a9abcf1f.png)
(3)已知点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/24a65f35281b21fdfaf7c437fbd321eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
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解题方法
2 . 如图某机器零件结构模型,中间最大球为正四面体
的内切球,中等球与最大球和正四面体三个面均相切,最小球与中等球和正四面体三个面均相切,已知正四面体
棱长为
,则模型中九个球的体积和为__________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b10e8abf8690e4b129466ddb918bcc94.png)
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3 . 已知球
与正方体
的各个面相切,平面
截球
所得的截面的面积为
,则正方体棱长为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e09725691ee7851f54c0dee86b2bf55.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f8d7771b82429dcd6b48b768918c7c3.png)
A.![]() | B.![]() | C.1 | D.2 |
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4 . 如图,在四棱锥
中,
平面
,
,且
,
是
的中点.
;
(2)若
,直线
与直线
所成角的余弦值为
.
(ⅰ)求直线
与平面
所成角;
(ⅱ)求二面角
的余弦值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80c753cb1eb73fd8d136d00462970797.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ce343ec5b0aa9ce4892fa682c614ba6.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a6164f6484b3b4acafcf1f3fd87ef196.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7d97dc3b752832906de41447bb58a341.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aaa42621cd6793e7f3673fdb49bc3123.png)
(ⅰ)求直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c09afc70f448545336304333d5b5658b.png)
(ⅱ)求二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c76abad7103e74e5613a802475f1c0f9.png)
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5 . 已知平面非零向量
的模均为
,若
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5085e3cdef9ea6c564e079f745d6fdb.png)
___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/799ad95449b4135dee2890ac31c43706.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc983f1bad03411ae64d84ff7bdf2551.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/91a16710403d8a87b858d92647ebaa1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5085e3cdef9ea6c564e079f745d6fdb.png)
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解题方法
6 . 设
,若对任意的
,都存在
,使得
成立,则
可以是( ).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ae470980d6e3b53c65b9d42d1f011c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef85b287d0fc9611ac7ba4bade11d864.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c24095e409b025db711f14be783a406c.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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解题方法
7 . 对任意两个非零向量
,定义
.若非零向量
,满足
,向量
与
的夹角是锐角,且
是整数,则
的取值范围是_____ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/662917aedec92809a13618093c8e0c3b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63c7ac4b4b9924ef29792fa6ac198f06.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4db35dbee504e3e66bfd03c24e4b7322.png)
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8 . 若函数
,则( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c2108d97caa96b493e77c070b60703ea.png)
A.![]() ![]() |
B.![]() ![]() |
C.![]() ![]() |
D.函数![]() ![]() |
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9 . 在边长为2的正方形
中,
,
分别为
,
的中点,沿
、
及
把这个正方形折成一个四面体,使得
、
、
三点重合于点
,得到四面体
,顶点
在底面
上的射影为
,下列结论正确的是( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
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A.![]() |
B.点![]() ![]() |
C.点![]() ![]() |
D.![]() |
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解题方法
10 . 已知平面向量
,
,且
,
,向量
满足
,则
取最小值时,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5085e3cdef9ea6c564e079f745d6fdb.png)
_________________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a2f4b1178f68bd147d1a2a6acd04435.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e5085e3cdef9ea6c564e079f745d6fdb.png)
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