解题方法
1 . 已知
,求证
.某同学解这道题时,注意到结论中的三个量
,
,
.由已知条件得到
,
,
.进一步发现三者的关系:
.又观察左边式子的结构发现就是两个数的倒数和,从而联想到以前做过的题目“已知
,
,求证
”,类比其解法得到题目的解法:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f60d4d44e161c4c3e151ad73024a8228.png)
,当且仅当
时取等号.所以
.求
的最小值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/497d269c30eec393e3f0e877ddbe2983.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/323f4e181b418a66cc36d75e0f8da126.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9f2416d1f75a45a314331146550832e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9db8d3facff8f90f28a936fc5b3ab878.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ea712984ea5017140e20bee226fd5af.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/481ee0d1e39e92a4732eea90225eb94c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/936553b69099e03189581a42a5c1d8aa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d6e90787c63ca5b5f1a45e0f6e85aaa1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0c05be59bdd7874fd8e9ee5ba5b17f4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94440d3e4c073f94f2b266ff99d50e74.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/67ca5fd57c2c2fcc3c7a574fdd1467d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/86546d8c56d9c72822cc2c834e240ad1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f60d4d44e161c4c3e151ad73024a8228.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55eb4703dc394b53fef7d12030c470d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/914c9d4dc14490413e77f6262d2a7aa9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/323f4e181b418a66cc36d75e0f8da126.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81e743594b98ac2006344494dddfb345.png)
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2 . 如图,已知
,作正方形ADEB,BFGC,CHIA.求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60c080f62063acfe028208d9b0b40cf4.png)
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3 . 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
|
630次组卷
|
4卷引用:黑龙江省大庆市大庆铁人中学2022-2023学年高一下学期期中数学试题
4 . 求证:方程
的两实根的平方和大于3的必要条件是
,这个条件是其充分条件吗?为什么?
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76294755a3ee79faec6c8ba0616f4b34.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54847462d4bf400f04e3dc4050f0bbdd.png)
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2023-05-26更新
|
160次组卷
|
2卷引用:1.2.1 必要条件与充分条件 -2021-2022学年高一上学期数学北师大版2019必修第一册
5 . 定义一种新运算
,满足
为非零实常数,对任意给定的
,设
,求证:数列
是等差数列.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fd94e5c210921dfbe11796b1fc97cee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2424a7811d45719824856e853176206.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/370a22338970ef057b14c64ea379494d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
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解题方法
6 . 如图所示圆锥
中,
为底面的直径.
分别为母线
与
的中点,点
是底面圆周上一点,若
,
,圆锥的高为
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/16/7e6c7737-8e52-4b2b-af91-453629c38943.png?resizew=160)
(1)求圆锥的侧面积
;
(2)求证:
与
是异面直线,并求其所成角的大小
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f9654c9824b84dce1f840e3414c47ddc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01c74a907dda6bb7d9d56d009d9df253.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0629ce42392a7fe9be21d25c39c3e64.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cdebc1592efdbdf58b9b0dd9ee725c32.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ff1c07d3ab5f594be5fffe13ebaaccb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/01961669cd597f61fa48e9853d678bb8.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/16/7e6c7737-8e52-4b2b-af91-453629c38943.png?resizew=160)
(1)求圆锥的侧面积
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
(2)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
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2022-12-15更新
|
857次组卷
|
2卷引用:上海市杨浦区2023届高三一模数学试题
7 . 已知
为直线
的方程,求证:不论
取何实数,直线
必过定点,并求出这个定点的坐标.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19944b6bee129bd8d8204ce01f71e714.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f0a532e15e232cb4b99a8d4d07c89575.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0f85fca60a11e1af2bf50138d0e3fe62.png)
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名校
8 . 如图,在
中,
为
边上一点,且
.
,求实数
、
的值;
(2)若
,求
的值;
(3)设点
满足
,求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3fe95f656b98b53f71a9d72bf0c9a4b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d71cde9bbb9c8fa969e04f8d0254eba7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/810633059a470392035aa375dfc20fd7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e06ca53803f042a5eca99f56a70f05e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d053b14c8588eee2acbbe44fc37a6886.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c77037587e3cc14dec8d74541341cbc1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7a66e27ef92fcc51530e54533e23973.png)
(3)设点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f6cfeef6dbc266f8ca53f78e7833e82d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29dfd8c22112c99c63890e79ecffa94f.png)
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2022-12-09更新
|
1774次组卷
|
10卷引用:上海市曹杨第二中学2021-2022学年高一下学期期末数学试题
上海市曹杨第二中学2021-2022学年高一下学期期末数学试题第9章《平面向量》单元达标高分突破必刷卷(基础版)第八章 向量的数量积与三角恒等变换(A卷·基础通关练)-【单元测试】2022-2023学年高一数学分层训练AB卷(人教B版2019必修第三册)第六章 平面向量及其应用(A卷·基础提升练)-【单元测试】2022-2023学年高一数学分层训练AB卷(人教A版2019必修第二册)(已下线)专题6.14 平面向量及其应用全章综合测试卷(基础篇)-2022-2023学年高一数学举一反三系列(人教A版2019必修第二册)江苏省盐城市东台创新高级中学2022-2023学年高一下学期2月月检测数学试题福建省宁德市福安市阳光国际集团福建区域联考2022-2023学年高一下学期期中数学试题广东省深圳市龙华外国语高级中学2023-2024学年高一下学期第一次段考数学试卷单元测试A卷——第六章?平面向量及其应用(已下线)上海市高一下学期期末真题必刷03-期末考点大串讲(沪教版2020必修二)
名校
9 . 如图,点C是AB的中点,AD=CE,CD=BE.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/26/89637958-251f-4726-8eb2-8c7f5e5a8466.png?resizew=186)
(1)求证:
;
(2)连接DE,求证:四边形CBED是平行四边形.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/26/89637958-251f-4726-8eb2-8c7f5e5a8466.png?resizew=186)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a60493fdc4350d34c12871c435f8160d.png)
(2)连接DE,求证:四边形CBED是平行四边形.
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10 . 如图,直线EF分别与直线AB、CD交于点E、F.EM平分
,FN平分
,
.求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea2ee75a234ac05a3225e49ddd8c5065.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7724af2445c723d1392aed54d210ed3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d5b3556dfd009e96e592ad2dda0dcf4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8a11029ca6b4b9e7f777af0280cf163c.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/16/14cbbb2f-07f7-4f2e-83bf-e940cd5823a9.png?resizew=211)
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