1 . 余弦定理是揭示三角形边角关系的重要定理,也是在勾股定理的基础上,增加了角度要素而成.而对三角形的边赋予方向,这些边就成了向量,向量与三角形的知识有着高度的结合.已知
,
,
分别为
内角
,
,
的对边:
(1)请用向量方法证明余弦定理
;
(2)若
,其中
为
边上的中线,求
的长度.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/071a7e733d466949ac935b4b8ee8d183.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
(1)请用向量方法证明余弦定理
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34369422d71dd95c61cdd1b8245d7b6c.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48897a577999a24e15e8645e7b23e592.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
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2023-06-11更新
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634次组卷
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4卷引用:黑龙江省双鸭山市第一中学2023-2024学年高一上学期期中数学试题
名校
解题方法
2 . 已知点
为线段
上的点,点
为
所在平面内任意一点,
,
,
,
,设
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/20/dbf32769-0600-418a-becc-15f28f50b0cd.png?resizew=193)
(1)求证:
,并求出
的值;
(2)若
,求
的面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/39acab3cfb59bfc9591371721ab01d93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca036d049f5205cf04cb1b9c5cd03f97.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85feff0ce62d9a89db8fc47b5952d5da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/262e062dcdd2039084a356862b123e9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bc48a3935a66d6fcdc0aaa3e6a331c38.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49128b2e5ecfd4aea19453f0bd52b3fa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/75fa3a75aacb99a46f46c229ec094a38.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/20/dbf32769-0600-418a-becc-15f28f50b0cd.png?resizew=193)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/34377f5318447ea6e2e7d5f4b126d5bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ccc2f02416db8211128e18af2d13ecf.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/12133283c743f2a43f0416beb30c1975.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2205cffebf8c4d5f81d15ed7b85c8936.png)
您最近一年使用:0次
2023-05-18更新
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527次组卷
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2卷引用:黑龙江省双鸭山市第一中学2023-2024学年高一上学期期中数学试题
名校
解题方法
3 . 平行四边形ABCD中,
,
,如图甲所示,作
于点E,将
沿着DE翻折,使点A与点P重合,如图乙所示.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/22/ff6f32a8-1ad4-4851-b013-3200acd67296.png?resizew=371)
(1)设平面PEB与平面PDC的交线为l,判断l与CD的位置关系,并证明;
(2)当四棱锥
的体积最大时,求二面角
的正切值;
(3)在(2)的条件下,G、H分别为棱DE,CD上的点,求空间四边形PGHB周长的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f80f51c31583fea58fde645474d60b8a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5595129319f9f5f069297ddb1455f97a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32c38dfd14dde969702dff97ef2270f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/22/ff6f32a8-1ad4-4851-b013-3200acd67296.png?resizew=371)
(1)设平面PEB与平面PDC的交线为l,判断l与CD的位置关系,并证明;
(2)当四棱锥
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e98920101c174b991d7a8481707ab88.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/715cc9ea5e7d80930284ffb117142770.png)
(3)在(2)的条件下,G、H分别为棱DE,CD上的点,求空间四边形PGHB周长的最小值.
您最近一年使用:0次
2022-06-20更新
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1456次组卷
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5卷引用:黑龙江省双鸭山市第一中学2021-2022学年高一下学期期末数学试题
4 . 已知数列
的前
项和为
,
,给出以下三个命题:
①
;②
是等差数列;③![](https://staticzujuan.xkw.com/quesimg/Upload/formula/28babe6d68eb0646f9e97bd9e01c3c86.png)
(1)从三个命题中选取两个作为条件,另外一个作为结论,并进行证明;
(2)利用(1)中的条件,证明数列
的前
项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/99aed0821e3241d550edfdc7c329cf50.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b065334d8f60c49f4bd3d9f1373fe4cd.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c6e35ba37b0cc1d390e05391554e9660.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/99aed0821e3241d550edfdc7c329cf50.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/28babe6d68eb0646f9e97bd9e01c3c86.png)
(1)从三个命题中选取两个作为条件,另外一个作为结论,并进行证明;
(2)利用(1)中的条件,证明数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7fa2c40028103fd23931f8772b0cefa9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c215db1d8f69757118ad405b78035628.png)
您最近一年使用:0次
2022-02-22更新
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680次组卷
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3卷引用:黑龙江省双鸭山市第一中学2021-2022学年高三上学期期末考试数学(理)试题
名校
5 . 已知直线l:
与直线l′:
相互垂直,圆C的圆心与点(2,1)关于直线l对称,且圆C过点M(-1,-1).
(1)求直线l与圆C的方程.
(2)过点M作两条直线分别与圆C交于P,Q两点,若直线MP,MQ的斜率满足kMP+kMQ=0,求证:直线PQ的斜率为1.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/217350dabb502a3b5fd1774cd9f11aaf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3f52cb58b6bc5d71030463ba7e28134.png)
(1)求直线l与圆C的方程.
(2)过点M作两条直线分别与圆C交于P,Q两点,若直线MP,MQ的斜率满足kMP+kMQ=0,求证:直线PQ的斜率为1.
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2021-08-28更新
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5卷引用:黑龙江省双鸭山市第一中学2023-2024学年高二上学期10月月考数学试题