如图,将矩形纸片ABCD(AD
AB)折叠,使点C刚好落在线段AD上,且折痕分别与边BC,AD相交于点E,F,设折叠后点C,D的对应点分别为点G,H.
(1)判断四边形CEGF的形状,并证明你的结论;
(2)若AB=4,且四边形CEGF的面积是20,求线段EF的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/392cdb9d30684cce244bef94b8d861b9.png)
(1)判断四边形CEGF的形状,并证明你的结论;
(2)若AB=4,且四边形CEGF的面积是20,求线段EF的长.
![](https://img.xkw.com/dksih/QBM/2020/10/21/2575534156242944/2579968718135297/STEM/e3b106a205134ed89f6b1feb4a52226a.png?resizew=212)
更新时间:2020-10-27 12:22:42
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解答题-证明题
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【推荐1】四边形
、
都是⊙
的内接四边形,
,
,
与
交于点
.
求证:
.
为了证明结论,小明进行了探索.请在下列框图中补全他的证明思路:
小明的证明思路
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2dde327febef2331a4766a79b433cc02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8ef3222a962b0a3b9bb1f4574b41bd79.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9390a8688fd466fb6b883b0d60dcd872.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6095bae4840bfa80f2468f94b2002d7b.png)
为了证明结论,小明进行了探索.请在下列框图中补全他的证明思路:
小明的证明思路
要证![]() ![]() 由已知条件①__________,易证 ![]() 故只要证②__________, 由已知条件 ![]() 故只要证 ![]() 由已知条件四边形 ![]() ![]() ![]() 易证 ![]() |
![](https://img.xkw.com/dksih/QBM/editorImg/2022/9/29/62a75f65-c9db-4010-83c5-a2a8691e7198.png?resizew=136)
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【推荐2】在下面的括号内,填上推理的根据.
已知:如图,
,
,求证:
.
证明![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c08980b6afedc04aa04f385791f0163.png)
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/758dc5363d5b601cd457da948795f951.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/998f0e4d57e343ff499c660d2059da15.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e262a1a3cf2d42d3834ce1ac084f6e9.png)
( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e8e3224fb15c22ad6770970da60ee80.png)
( )
( )
已知:如图,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e53497af8899cb299d762f1a4f46a55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3e9af77ba220f7fbc983ba79dd40483.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05a39f26bb5b2270bdf078e16c5c5693.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/10/30/a580d599-0924-480c-b466-213f93cdee1f.png?resizew=216)
证明
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7c08980b6afedc04aa04f385791f0163.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba02910a01689f636c71116e96dfdf33.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/758dc5363d5b601cd457da948795f951.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/998f0e4d57e343ff499c660d2059da15.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e262a1a3cf2d42d3834ce1ac084f6e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/010e3be218f4dfe4b04bb5596b265b73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e8e3224fb15c22ad6770970da60ee80.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/329a673b9019f8c73591b5c978bcdbb0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a01ef689f7d0805d53969ee1cd667bb5.png)
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【推荐1】如图,在四边形ABCD中,AB∥DC,AB=AD,对角AC、BD交于点O,AC平分∠BAD.
(2)过点C作CE⊥AB交AB的延长线于点E,若AB=13,BD=10,求CE的长.
(2)过点C作CE⊥AB交AB的延长线于点E,若AB=13,BD=10,求CE的长.
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【推荐2】已知:如图1,
中,∠ABC与∠ACB的角平分线交于点D,过点D作
交AB于点E,交AC于点F.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/24/47ad37b2-4a6d-4b1e-83da-d29623fd872b.png?resizew=319)
(1)求证:BE+CF=EF;
(2)若将已知条件中的“∠ACB的角平分线”改为“∠ACB的外角平分线”,其他条件不变(如图2)(1)中的结论是否仍然成立?若成立,请给予证明;若不成立,请写出BE,CF,EF之间的关系.(不需证明)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f80f699558ff62a31152df321b064f0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee73452ee4d5437f1399f1235b95e55f.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/24/47ad37b2-4a6d-4b1e-83da-d29623fd872b.png?resizew=319)
(1)求证:BE+CF=EF;
(2)若将已知条件中的“∠ACB的角平分线”改为“∠ACB的外角平分线”,其他条件不变(如图2)(1)中的结论是否仍然成立?若成立,请给予证明;若不成立,请写出BE,CF,EF之间的关系.(不需证明)
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【推荐3】(1)如图 1,在△ABC 中,∠ABC 的平分线 BF 交 AC 于 F, 过点 F 作 DF∥BC, 求证:BD=DF.
(2)如图 2,在△ABC 中,∠ABC 的平分线 BF 与∠ACB 的平分线 CF 相交于 F,过点 F 作 DE∥BC,交直线 AB 于点 D,交直线 AC 于点 E.那么 BD,CE,DE 之间存在什么关系?并证明这种关系.
(3)如图 3,在△ABC 中,∠ABC 的平分线 BF 与∠ACB 的外角平分线 CF 相交于 F,过点 F 作 DE∥BC,交直线 AB 于点D,交直线 AC 于点 E.那么 BD,CE,DE 之间存在什么关系?请写出你的猜想.(不需证明)
(2)如图 2,在△ABC 中,∠ABC 的平分线 BF 与∠ACB 的平分线 CF 相交于 F,过点 F 作 DE∥BC,交直线 AB 于点 D,交直线 AC 于点 E.那么 BD,CE,DE 之间存在什么关系?并证明这种关系.
(3)如图 3,在△ABC 中,∠ABC 的平分线 BF 与∠ACB 的外角平分线 CF 相交于 F,过点 F 作 DE∥BC,交直线 AB 于点D,交直线 AC 于点 E.那么 BD,CE,DE 之间存在什么关系?请写出你的猜想.(不需证明)
![](https://img.xkw.com/dksih/QBM/2020/4/14/2441275370496000/2441628565020672/STEM/06af5c710deb4fcfbec60468a35d0bf6.png?resizew=424)
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【推荐1】如图,OABC是一张放在平面直角坐标系中的矩形纸片,O为原点,点A在x轴的正半轴上,点C在y轴的正半轴上,OA=5,OC=4,在OC边上取一点D,将纸片沿AD翻折,使点O落在BC边上的点E处,求D,E两点的坐标.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/13/d414af85-0893-4740-8e2b-019bae5d8c4e.png?resizew=187)
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【推荐2】如图,在矩形中,
,对角线
相交于点
,点
从点
出发沿
方向向点
匀速运动,速度为
,点
同时从
出发,沿
方向向点
匀速运动,速度为
.过点
作
交
边于点
,交
边于点
,连接
并延长,交
于
,连接
.设运动时间为
.
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ed283a253b61df01f2a1cdc0cd8003f3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
(2)设四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/db492efc6bfe199d47633e6d5946ad57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fb194fd63b75af067ba10dee7471d299.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf231f8f86fb922df4ca0c87f044cec3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
(3)是否存在某一时刻
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d3f6710dda2de3a067589017798a716c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2dca049735b45fb9b2533c68605eddc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36a1b09c653185842513e24ebba60bb3.png)
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【推荐1】如图1,
的对角线
,
相交于点
,且
,
,
.
是菱形;
(2)如图2,若
,
,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5138a9f70d5e8b0580e30fef6eb7baef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3aafd2e9983c478261f5d6cd8d5c027.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09d1ee2efdb2c3b7c90198efc88010db.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cede2006bf19da5ae1c126da517ce79c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(2)如图2,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a58a622e2b1a239f2f96aa1501e9799.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc11331a7b2d2619b40ee6d34c3bd620.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
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【推荐2】如图,在
中,
,线段
的垂直平分线交
于
点,交
于
点,过点
作
的平行线交直线
于
点,连接
,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/4/25eb9788-1454-442c-a71f-87eeaa11237d.png?resizew=181)
(1)求证:四边形
是菱形;
(2)若
,
,求菱形
的面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c06154cae3bf7a8ce5a1e97a7380875.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.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/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21037e170bdbb322558e79c40c00b454.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/4/25eb9788-1454-442c-a71f-87eeaa11237d.png?resizew=181)
(1)求证:四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/910936ec9fb419d51ce2f5ea817f8401.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc34db5860990e51ba31edc8cdd077c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/392b9e1a179a6676362679354a9e7e51.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/910936ec9fb419d51ce2f5ea817f8401.png)
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