阅读下面材料:
数学课上,老师给出了如下问题:
如图,AD为△ABC中线,点E在AC上,BE交AD于点F,AE=EF.求证:AC=BF.
![](https://img.xkw.com/dksih/QBM/2021/1/29/2646698217029632/2649408280059904/STEM/cff02581-b879-4fd8-bbd3-369b91760e36.png)
经过讨论,同学们得到以下思路:
完成下面问题:
(1)这一思路的辅助线的作法是: .
(2)请你给出一种不同于以上思路的证明方法(要求:写出辅助线的作法,画出相应的图形,并写出证明过程).
数学课上,老师给出了如下问题:
如图,AD为△ABC中线,点E在AC上,BE交AD于点F,AE=EF.求证:AC=BF.
![](https://img.xkw.com/dksih/QBM/2021/1/29/2646698217029632/2649408280059904/STEM/cff02581-b879-4fd8-bbd3-369b91760e36.png)
经过讨论,同学们得到以下思路:
如图①,添加辅助线后依据SAS可证得△ADC≌△GDB,再利用AE=EF可以进一步证得∠G=∠FAE=∠AFE=∠BFG,从而证明结论.![]() |
(1)这一思路的辅助线的作法是: .
(2)请你给出一种不同于以上思路的证明方法(要求:写出辅助线的作法,画出相应的图形,并写出证明过程).
20-21八年级上·河南信阳·期末 查看更多[2]
更新时间:2021-02-02 14:57:51
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【推荐1】如图在△AOB和△COD中,OA=OB,OC=OD,OA=OC,∠AOB=∠COD=36°.连接AC、BD交于点M,连接OM.
(l)求∠AMB的度数;
(2)MO是∠AMD的角分线吗?请说明理由.
(l)求∠AMB的度数;
(2)MO是∠AMD的角分线吗?请说明理由.
![](https://img.xkw.com/dksih/QBM/2021/12/10/2869428744069120/2877486724145152/STEM/871c5e59-150d-4062-b177-5095f172d541.png?resizew=256)
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【推荐2】如图所示,在平面直角坐标系中,
轴于点B,
轴于点D.点
,
,且a,b满足
.
(1)如图1,求证:
;
(2)如图1,若
,在x轴上是否存在点F,使
是以CO为腰的等腰三角形?若存在,求出点F的坐标;若不存在,请说明理由;
(3)如图2,连接AC,BD交于点P,求证:点P为AC中点.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2ea84cba8ccd585ad1da1fd204bc3e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2634263d383b0487281fdcf6fe3cc625.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94953cf5a25d8337393232c485dcf150.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1d832f64a2e282b4bd09d957b703c0da.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/783b7700451f22555650af500b2c2e87.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/9/11/29c689f3-79d8-492e-b438-2bbe9a2795c2.png?resizew=341)
(1)如图1,求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f543812258a6a92724d3f88810f7402.png)
(2)如图1,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/941d4f0c967b27482dec4e8dfbb40d4d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a54de7e539151a11b1aeed986057c6b5.png)
(3)如图2,连接AC,BD交于点P,求证:点P为AC中点.
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【推荐1】【背景问题】
课外兴趣小组活动时,老师提出了如下问题:
如图1,
中,
是
边上的中线,若
,求边
的取值范围.
至点
,使
,连接
.请根据小明的方法思考:
(1)由已知和作图能得到
,依据是______.
A.
B.
C.
D.![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d5eb2decaa6be2df36a5e4b7fabf585d.png)
(2)由“三角形的三边关系”可求得边
的取值范围是___ .
解后反思:题目中出现“中点”、“中线”等条件,可考虑延长中线构造全等三角形,把分散的已知条件和所求证的结论集中到同一个三角形之中.
【感悟方法】
(3)如图2,
是
的中线,
交
于
,交
于
,
.求证:
.
课外兴趣小组活动时,老师提出了如下问题:
如图1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/71d7f12ff280c7eebd79c494e6b99818.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0ad98ad714864041a632ca949308e417.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
(1)由已知和作图能得到
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed22093ece26eca6dfdb31d58698c929.png)
A.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6720e36b02193db161c61d4017673760.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5a290f047f50481318d040c604d72f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9beb8b968744573e593ac28451c69729.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d5eb2decaa6be2df36a5e4b7fabf585d.png)
(2)由“三角形的三边关系”可求得边
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
解后反思:题目中出现“中点”、“中线”等条件,可考虑延长中线构造全等三角形,把分散的已知条件和所求证的结论集中到同一个三角形之中.
【感悟方法】
(3)如图2,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a5787c784b686435a2073bdeb836307c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3767efa8adfb71001ad39df9560cbf6a.png)
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解答题-计算题
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【推荐2】综合与实践
小明遇到这样一个问题,如图1,
中,
,
,点
为
的中点,求
的取值范围.小明的做法是:如图2,延长
到
,使
,连接
,构造
,经过推理和计算使问题得到解决.
请回答:
(1)小明证明
用到的判定定理是: ;
.
.
.
.![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4351a730f61bb998bab8f0b7848912d7.png)
(2)
的取值范围是 .
小明总结:倍长中线法最重要的一点就是延长中线一倍,完成全等三角形模型的构造.
参考小明思考问题的方法,解决问题:
(3)如图3,在正方形
(各角都为直角)中,
为
边的中点,
、
分别为
边上的点,若
,
,
,求
的长.
小明遇到这样一个问题,如图1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/16e0c5cb53fd85b7a23f0580df6bb49a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c3ad4c0ba3a6750537789844d0ec419d.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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0ad98ad714864041a632ca949308e417.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/440095115d64b74e4b1c30e402c178e1.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/13/3534a523-a1d9-430f-a087-7f927e2bf27b.png?resizew=427)
请回答:
(1)小明证明
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/440095115d64b74e4b1c30e402c178e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5a290f047f50481318d040c604d72f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6720e36b02193db161c61d4017673760.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9beb8b968744573e593ac28451c69729.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4351a730f61bb998bab8f0b7848912d7.png)
(2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
小明总结:倍长中线法最重要的一点就是延长中线一倍,完成全等三角形模型的构造.
参考小明思考问题的方法,解决问题:
(3)如图3,在正方形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb6cee83d36c4da913e0790e5070c46f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6402c0f9eecfcdf73f9e87ca82a6f2c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5eba8bf0c4a8e49b3fac25832a0b0005.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0e57a13c665af88f326c9890072bf73.png)
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【推荐3】阅读下列材料:
小明遇到这样问题:
如图1,在
中,
,在AB上取一点D,在AC延长线上取一点E,若
,判断PD与PE的数量关系.
小明通过思考发现,可以采用两种方法解决问题:
方法一:过点D作
,交BC于F,即可解决问题;
方法二:过点D、点E分别向直线BC引垂线,垂足分别是F、G,也可解决问题.
请回答:PD与PE的数量关系是______;
任选上述两种方法中的一种方法,在图1中补全图象,并给出证明;
参考小明思考问题的方法,解决问题:
如图2,在
中,
,将AC绕点A顺时针旋转
度后得到AD,过点D作
,交AB于点E,
,则图中是否存在与DE相等的线段,请找出来并给出证明.
小明遇到这样问题:
如图1,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ab41054fa9ce51b68e78d9c0cf398d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb7852eb99a283b8f0bd5a4dff3c2def.png)
小明通过思考发现,可以采用两种方法解决问题:
方法一:过点D作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e7f0e21c88d99d25c0e4af0d8bd7bd2.png)
方法二:过点D、点E分别向直线BC引垂线,垂足分别是F、G,也可解决问题.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4141b26d2c32655003494a91ad6331b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65863c1abad833b79c303bfca24f535c.png)
参考小明思考问题的方法,解决问题:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4bb89a362c1faf4d0c306eabbb59710.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3cec18de87c5ab41987368fdf4b6f884.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b90e77a94e54755c4d0c93bc98e8a9ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48784d57f741f6097722578f984fc6f9.png)
![](https://img.xkw.com/dksih/QBM/2019/3/11/2158145068687360/2159599035842560/STEM/4e536923315042f4bdd9a5c6e23aa87e.png?resizew=411)
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【推荐1】如图1,在锐角△ABC中,∠ABC=45°,高线AD、BE相交于点F.
(1)判断BF与AC的数量关系并说明理由.
(2)如图2,将△ACD沿线段AD对折,点C落在BD上的点M,AM与BE相交于点N,当DE∥AM时,
①求证:AE=EC;
②直接写出∠MAC的度数以及线段NE与AC的数量关系.
(1)判断BF与AC的数量关系并说明理由.
(2)如图2,将△ACD沿线段AD对折,点C落在BD上的点M,AM与BE相交于点N,当DE∥AM时,
①求证:AE=EC;
②直接写出∠MAC的度数以及线段NE与AC的数量关系.
![](https://img.xkw.com/dksih/QBM/2019/2/2/2132045263077376/2137215396118528/STEM/b5880c89ed8648e698767e88e173b86b.png?resizew=359)
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【推荐2】如图,在Rt△ABC中,∠ACB=90°,CD为AB上的高,AF为∠BAC的角平分线,AF交CD于点E,交BC于点F.
![](https://img.xkw.com/dksih/QBM/2021/12/21/2877140616519680/2880865130061824/STEM/ada303c6-a376-42ee-8dd6-528dd7dc01ee.png?resizew=618)
(1) 如图1,①∠ACD ∠B(选填“<,=,>”中的一个)
②如图1,求证:CE=CF;
(2) 如图1,作EG∥AB交BC于点G,若AD=a,△EFG为等腰三角形,求AC(含a的代数式表示);
(3)如图2,过BC上一点M,作MN⊥AB于点N,使得MN=ED,探索BM与CF的数量关系.
![](https://img.xkw.com/dksih/QBM/2021/12/21/2877140616519680/2880865130061824/STEM/ada303c6-a376-42ee-8dd6-528dd7dc01ee.png?resizew=618)
(1) 如图1,①∠ACD ∠B(选填“<,=,>”中的一个)
②如图1,求证:CE=CF;
(2) 如图1,作EG∥AB交BC于点G,若AD=a,△EFG为等腰三角形,求AC(含a的代数式表示);
(3)如图2,过BC上一点M,作MN⊥AB于点N,使得MN=ED,探索BM与CF的数量关系.
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