名校
1 . 设函数
定义域为
.若整数
满足
,则称
与
“相关”于
.
(1)设
,
,写出所有与
“相关”于
的整数;
(2)设
满足:任取不同的整数
,
与
均“相关”于
.求证:存在整数
,使得
都与
“相关”于
;
(3)是否存在实数
,使得函数
,
满足:存在
,能使所有与
“相关”于
的非零整数组成一个非空有限集?若这样的
存在,指出
和
的大小关系(无需证明),并求出
的取值范围;若这样的
不存在,说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0afb80007983e5b99dcdeebf87d18ff4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cae7b35b6dbdeafb82810fb8239121c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b056a90a2751f04ba5fff3dc5c1d0674.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d53f0be9e922c54b74dc21ef147d81c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5873c01192b7d33b7483f444f90b5b0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
(1)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f713f92ce74aa961b391fe544e609a68.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e196c4f6545854d1fee5fea9609d01d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0afb80007983e5b99dcdeebf87d18ff4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6cec48f249cb8141bad725728996fbf4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5873c01192b7d33b7483f444f90b5b0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0becd5c2342ac2cef8d24b6e7e8a0abc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f4b983d54b0b2d085456306ef564bda.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8e8936c9fe1e81726455908657a29fc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
(3)是否存在实数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7489d1555eaffa5d7d26d37df5d4355a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e196c4f6545854d1fee5fea9609d01d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8380733ca1aaccc36e3b0c658bd6011b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/79b752f0f189e5d8666daea73e145dff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cee175df20c19745745059464e643079.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c95b6be4554f03bf496092f1acdfbb89.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
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2 . 如图所示,四边形
为梯形,
,
,
,以
为一条边作矩形
,且
,平面
平面
.
;
(2)甲同学研究发现并证明了这样一个结论:如果两个平面所成的二面角为
,其中一个平面内的图形
在另一个平面上的正投影为
,它们的面积分别记为
和
,则
.乙同学利用甲的这个结论,发现在线段
上存在点
,使得
.请你对乙同学发现的结论进行证明.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10df84d553a8826a7ce9bff4bf0d95b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcd0ced286a0fbc7e4862f8147264277.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a75b1354b8b783a65ee5e3bc596a976.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6bbc56d42b003cbcb1fbe5c50e55b26b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3362a45b72536c714c5107b0ae94f1c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c0db1f4f666a9be9ede868065a50997.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31025539da369c563e8633f375146593.png)
(2)甲同学研究发现并证明了这样一个结论:如果两个平面所成的二面角为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c5a434a89f3f689db2a4623efbc74a7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81722445de00f3cfcc3cb97e45b0d8dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e27e50f80b7bf7025a049692b17abcd8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fbce6d96030ceae48cfef1634085c88.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3effb95a6c4422798440cd8a2a110636.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c8c820f511d3b23ffebae3822f19589.png)
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名校
3 . (1)在用“五点法”作出函数
的大致图象的过程中,第一步需要将五个关键点列表,请完成下表:
(2)设实数
且
,求证:
;(可以使用公式:
)
(3)证明:等式
对任意实数
恒成立的充要条件是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/467a953b54798b6e2dcd6d76f8817938.png)
0 | |||||
0 | |||||
1 |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94440d3e4c073f94f2b266ff99d50e74.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c400a615a16a1662de98dfb4e49d58d3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d95727eed094e7ceb6663ee9d39bda3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/141ba74bc522b95958aea59cdc8c93d0.png)
(3)证明:等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c83576aaf57c7ebdcf56110fdbb0c12a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1d8ae1706a9ea5df3eca17eaa5c8b71.png)
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名校
4 . 在平面直角坐标系xoy中,已知
,圆C:
与x轴交于O ,B.
(1)证明:在x轴上存在异于点A的定点
,使得对于圆C上任一点P,都有
为定值;
(2)点M为圆C上位于x轴上方的任一点,过(1)中的点
作垂直于x轴的直线l,直线OM与l交于点N,直线AN与直线MB交于点R,求证:点R在椭圆上运动.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5cd99c5000629d7f49499d666e68f40d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6316e0e6da742e9b035d8f2cc91a4dd.png)
(1)证明:在x轴上存在异于点A的定点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/439e95540157803d4ac3cf61a49f50a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c7383714dc2ac9fe164e26a4d1bbd0c.png)
(2)点M为圆C上位于x轴上方的任一点,过(1)中的点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/439e95540157803d4ac3cf61a49f50a8.png)
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解题方法
5 . 如图,在四棱锥
中,侧棱
平面
,底面四边形
是矩形,
,点
、
分别为棱
、
的中点,点
在棱
上.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/4/17/feb0307f-0b41-42a8-8cf5-9a37f9538ba6.png?resizew=175)
(1)若
,求证:直线
平面
;
(2)若
,从下面①②两个条件中选取一个作为已知,证明另外一个成立.
①平面
与平面
的交线为直线
,
与直线
成角的余弦值为
;
②二面角
的余弦值为
.
注:若选择不同的组合分别作答,则按第一个解答计分.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5164a3cc47e266446d49127e2ef10c37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21f9157fce2a8339d281178c7c0bccbe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fa7bbd7831e9ff4f8cffc8889d34f05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2fa7bbd7831e9ff4f8cffc8889d34f05.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/888d60eea4792374fda946b0a7b2831c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/4/17/feb0307f-0b41-42a8-8cf5-9a37f9538ba6.png?resizew=175)
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f10d00f6d7d9019f8b964bd4e19d629a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/982d01f052709b72afeaf1015fc7acc8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/149596fee6ed1e2d19fd8dadc14a8baf.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef0402dd5ae3db10281f9f1e11738bcb.png)
①平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9a32bd7a1b78b5a0ec562c4025aea8c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9868f77d5ab5073b6145f1c6d272122e.png)
②二面角
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/42f1b90a3031fcd75754365a32b65a6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/64f1145c162038df3c7184d9201c628e.png)
注:若选择不同的组合分别作答,则按第一个解答计分.
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解题方法
6 . 如图所示,已知
是圆锥
底面的两条直径,
为劣弧
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/14/3680e51f-a0cf-4694-ad1c-2e7d3247ddc6.png?resizew=181)
(1)证明:
;
(2)若
,
为线段
上的一点,且
,求证:平面![](https://staticzujuan.xkw.com/quesimg/Upload/formula/500df0e782bb081e608f4bc1d576afcf.png)
平面
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73b3c032441543354c154ee67d744abb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/18e5ef91fb27dd684a27ae7f1993cfba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed41d321f4c0717ac5b443aad942d9a7.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/14/3680e51f-a0cf-4694-ad1c-2e7d3247ddc6.png?resizew=181)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57b5a1af8b3b2a97aae1eba18da26bc7.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/782920f4bbf8967c7379f1f83540c3b6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fddbb7f29e8672f34941fe70b0a1e45f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13e1f96727b692b469d48c01c1b0268c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/500df0e782bb081e608f4bc1d576afcf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/638537c0a30676c73fea76c80e0f8bd0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d923a338dd2d2e29336b42574d38448.png)
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7 . 下图是小明复习全等三角形时遇到的一个问题并引发的思考,请帮助小明完成以下学习任务.
如图,OC平分
,点P在OC上,M、N分别是
、OB上的点,
,求证:
.
小明的思考:要证明
,只需证明
即可.
证法:如图①:∵OC平分
,∴
,
又∵
,
,∴
,
∴
;
请仔细阅读并完成以下任务:
![](https://img.xkw.com/dksih/QBM/2022/5/3/2971556652843008/2974950110486528/STEM/93b06bfd-3171-47a5-9d77-19e02cb916d0.png?resizew=524)
(1)小明得出
的依据是______(填序号).
①SSS ②SAS ③AAS ④ASA ⑤HL
(2)如图②,在四边形ABCD中,
,
的平分线和
的平分线交于CD边上点P,求证:
.
(3)在(2)的条件下,如图③,若
,
,当△PBC有一个内角是45°时,
的面积是______.
如图,OC平分
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d7b2fe01a33c4825f9974ed9663a99c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef4113c492885ba7c47fe42ac792578f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2032fccdf9ab12429aae024d67b19d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4acd79bb9fb06f7c806eb6e17e4b613.png)
小明的思考:要证明
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4acd79bb9fb06f7c806eb6e17e4b613.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94d54326f92838c51a197cc82985e506.png)
证法:如图①:∵OC平分
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d7b2fe01a33c4825f9974ed9663a99c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c1f18cef1745d84a0265246684753bd.png)
又∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25ce5cddb3791c46d6ef0c32d35a7886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2032fccdf9ab12429aae024d67b19d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/905a8192e8d6365309562606283e9959.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4acd79bb9fb06f7c806eb6e17e4b613.png)
请仔细阅读并完成以下任务:
![](https://img.xkw.com/dksih/QBM/2022/5/3/2971556652843008/2974950110486528/STEM/93b06bfd-3171-47a5-9d77-19e02cb916d0.png?resizew=524)
(1)小明得出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/905a8192e8d6365309562606283e9959.png)
①SSS ②SAS ③AAS ④ASA ⑤HL
(2)如图②,在四边形ABCD中,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/609ada36dd56b33279103ebc1f90bbac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4189a0821a0ffab9dc171ecd279ba442.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d39b8d91afc34e4a9b0fdbb6bafb9087.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ed66431681da1db8f7cb0f40cd19201.png)
(3)在(2)的条件下,如图③,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc34db5860990e51ba31edc8cdd077c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/afcd54ff42ebdc70cb273cd5909d549f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55a675310c8ba418e5a59beb7317e21e.png)
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8 . 请阅读下列材料,并完成相应的任务.
战国时的《墨经》就有“圆,一中同长也”的记载.与圆有关的定理有很多,弦切角定理就是其中之一.我们把顶点在圆上,一边和圆相交,另一边和圆相切的角叫做弦切角.弦切角定理:弦切角的度数等于它所夹的弧所对的圆周角度数.
下面是弦切角定理的部分证明过程:
证明:①如图1,AB与
相切于点A.当圆心O在弦AC上时,容易得到
,所以弦切角
.
②如图2,AB与
相切于点A.当圆心O在
的外部时,过点A作直径AF交
于点F,连接FC.
∵AF是直径,∴
,∴
.
∵AB与
相切于点A,∴
,∴
,∴
.
![](https://img.xkw.com/dksih/QBM/2022/5/3/2971556652843008/2974950109806592/STEM/e34e22f97b164f5baf07d88ddab505fe.png?resizew=554)
(1)如图3,AB与
相切于点A,当圆心O在
的内部时,过点A作直径AD交
于点D,在
上任取一点E,连接EC,ED,EA,求证:
;
(2)如图3,已知
的半径为1,弦切角
,求
的长.
战国时的《墨经》就有“圆,一中同长也”的记载.与圆有关的定理有很多,弦切角定理就是其中之一.我们把顶点在圆上,一边和圆相交,另一边和圆相切的角叫做弦切角.弦切角定理:弦切角的度数等于它所夹的弧所对的圆周角度数.
下面是弦切角定理的部分证明过程:
证明:①如图1,AB与
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c10d461a7c0b86a2f09c2ea17f38260e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/460511579aaa077d85fe53f6bb7772d5.png)
②如图2,AB与
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cbce11aa19b8bd2bf6ee5a834e005de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
∵AF是直径,∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e23d90078fcdfde7e9f221bc2bebda3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/da32065b24911b830aaa9095edee6461.png)
∵AB与
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d89c5a162bd71f3b237d18d0996a6d73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f36c57e73133469b27213ab57ce710c1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49db80c5a4f32fcd2db22bf6903ea481.png)
![](https://img.xkw.com/dksih/QBM/2022/5/3/2971556652843008/2974950109806592/STEM/e34e22f97b164f5baf07d88ddab505fe.png?resizew=554)
(1)如图3,AB与
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7cbce11aa19b8bd2bf6ee5a834e005de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/667349d99185bb045030b733352ff7fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0bce8c7f984ded4431266d97ded4523c.png)
(2)如图3,已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5dbebd2e0b7ee2dae2612c3de832a543.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/667349d99185bb045030b733352ff7fd.png)
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解题方法
9 . 在钝角
中,三个内角为A,B,C,满足
.
(1)证明:
是等腰三角形;
(2)若延长
至D点,使得
,且
,求证:
为定值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c7cfa8af7b3ed2577c53b6ca8965b50.png)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
(2)若延长
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35333abd7f02d663d15251bc5cbbf921.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/833cfda415649b832cc136caed392753.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2520e34084c7686762c476b60015b28.png)
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名校
解题方法
10 . 如图,四面体
的每条棱长都等于2,
分别是棱
的中点,
分别为面
,面
,面
的重心.
面
;
(2)求平面
与平面
的夹角的余弦值;
(3)保持点
位置不变,在
内(包括边界)拖动点
,使直线
与平面
平行,求点
轨迹长度;
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07ae3327287e5093b663e96e8f9dcbb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5262192e49cf903ee094457dbc250f96.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c7d9bc3fdf89de0b8e725961f8ddc096.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca67a5b8f69507c8b80379e86f90a8ce.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4eb7e9ad5486cf1c5e506b20c5469e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e388bba4de84bc9d6919cb6aa9b72447.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7abd284f76d9f5769bc189508ce2572b.png)
(2)求平面
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a0f9bc9123d19a09babe8609cf12327.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6684d8fe0d6da7564247e47b948e3997.png)
(3)保持点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a373959bb9026f8a09845c0b828bf82.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/661ff55b5ebbadfb600989af3cfce2fd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a0f9bc9123d19a09babe8609cf12327.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
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