阅读理解:小明热爱数学,在课外书上看到了一个有趣的定理——“中线长定理”:三角形两边的平方和等于第三边的一半与第三边上的中线的平方和的两倍.如图1,在
中,点 D 为
的 中 点 ,根据“中线长定理”,可得:
.
小明尝试对它进行证明,部分过程如下:
解:过点A作
于点E,如图2,在
中,
,
同理可得:
,
,
为证明的方便,不妨设
,
,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfcda9fd861fdc6cc604cbeef7d6e8f2.png)
(1)请你完成小明剩余的证明过程;
(2)在
中,点D为
的中点,
,
,
,求
的长;
(3)如图3,
的半径为6,点A在圆内,且
,点B和点C在
上,且
,点E、F分别为
、
的中点,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51056472e8bc2ac5deb51b218b8e8dfd.png)
小明尝试对它进行证明,部分过程如下:
解:过点A作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e3f5dc11efe60b4fd9a13b1d6b83842.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1a3b94566843e92ce775ff6bdf386fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e4ac0d942636f956146beb37e61ecbf.png)
同理可得:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/001e843fcc05f3e39aeea1e407f7630c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/84bc23a1ff4ecafd57913425a1f1c14f.png)
为证明的方便,不妨设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3d6ee95e7130903b3a30b3bca0273c8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a5d70e5d13db498f1c8a2e017c56e58b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfcda9fd861fdc6cc604cbeef7d6e8f2.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/3/19/8f562b2b-bb21-4eb8-96ee-a50c0861a1c8.png?resizew=381)
(1)请你完成小明剩余的证明过程;
(2)在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/305a88d4e0249bd16d48eda01331d2d4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8a7b5adfcac0f46a4cd19da4ebb4a2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07140f277a35733d8c97577ccdd4e3ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
(3)如图3,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e001897d70ceee81406f3b01d284b83b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c06154cae3bf7a8ce5a1e97a7380875.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2c3d2cba96f6f03520c0b3f6e4da03e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
更新时间:2024-03-20 09:58:35
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解题方法
【推荐1】如图所示,在△ABC中,AB=5,AC=13,BC边上的中线AD=6,求BC的长.
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【推荐2】如图,方格纸中每个小正方形的边长都是1,△ABC的顶点都在小正方形的顶点处,将△ABC平移后得到
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(1)在给定的方格纸中画出平移后的
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【推荐1】在平面直角坐标系中,
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d572eb3233343b90f190dde56701f22b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49cba284d675a3028d7a8d54f1f8ae70.png)
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(2)如图②,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/97cf714ffb3fd5917a76b191640b55fe.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1934eb2d22fad324650fd0835061de8e.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/5/25/cc9b00d1-4748-4913-a918-64218913e049.png?resizew=171)
(1)求证:四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8bc1cbcd6d00f0c36bad8254297d9f33.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07160f14b3b453bebb64cb2bf96dc85a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c8832c5450a61500ccbf73d95e16f449.png)
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【推荐2】类比、转化、分类讨论等思想方法和数学基本图形在数学学习和解题中经常用到,如下是一个案例,请补充完整.
![](https://img.xkw.com/dksih/QBM/2022/12/19/3134244758528000/3139880573755392/STEM/c83cf74492c641c9938350d9647d6fea.png?resizew=448)
(1)原题:如图1,在
中,
是直径,
于点B,
于点D,
,
,
,则
= .
(2)尝试探究:如图2,在
中,
是直径,
于点B,
于点D,点E在
上,
,
,
,
,则
= (写出解答过程).
(3)类比延伸:利用图3,再探究,当
两点分别在直径
两侧,且
,
于点B,
于点D,
时,则线段
满足的数量关系为 .
![](https://img.xkw.com/dksih/QBM/2022/12/19/3134244758528000/3139880573755392/STEM/c83cf74492c641c9938350d9647d6fea.png?resizew=448)
(1)原题:如图1,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c1be642ddd61c3ad26bcbe2dc42e3512.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a1fbbed1dbff0bdf2de260443749e151.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60096d11a222426d712390d3aad75ff7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/efc6e4b936d7a800e839a30c3839574d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e673ef2d48215ca84a48377f17d6df00.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
(2)尝试探究:如图2,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
(3)类比延伸:利用图3,再探究,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/62e478787ebfeb68a5a7594dbd9eecd4.png)
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