将长方形纸片,按下列要求折叠.并回答问题1,2,3;
【折叠一】
第1步:将长方形纸片,按图1所示的方法折叠;
第2步:按图2所示的方法折叠;
第3步:将图形展开,如图3,在长方形ABCD中,EF,GD为折叠过程中产生的折痕
问题1:EF与GD平行?请说明理由.
【折叠二】
第1步:将长方形纸片,按图4所示的方法折叠;
第2步:按图5所示的方法折叠;
第3步:将图形展开,如图6,将长方形ABCD中,EF,GH为折叠过程中产生的折痕.
问题2:EF与GH平行吗?请说明理由.
问题3:如图7,在【折叠二】中,若纸片的长为16厘米,宽为2厘米,则阴影部分面积的最大值为________.
【折叠一】
第1步:将长方形纸片,按图1所示的方法折叠;
第2步:按图2所示的方法折叠;
第3步:将图形展开,如图3,在长方形ABCD中,EF,GD为折叠过程中产生的折痕
问题1:EF与GD平行?请说明理由.
【折叠二】
第1步:将长方形纸片,按图4所示的方法折叠;
第2步:按图5所示的方法折叠;
第3步:将图形展开,如图6,将长方形ABCD中,EF,GH为折叠过程中产生的折痕.
问题2:EF与GH平行吗?请说明理由.
问题3:如图7,在【折叠二】中,若纸片的长为16厘米,宽为2厘米,则阴影部分面积的最大值为________.
![](https://img.xkw.com/dksih/QBM/2020/8/18/2530610545147904/2531406905401345/STEM/e0df3534-b914-4b02-b946-cbc43aad07ff.png)
更新时间:2020-08-19 21:43:26
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【推荐1】已知,如图,AD∥BE,C为BE上一点,CD与AE相交于点F,连接AC.∠1=∠2,∠3=∠4.
(1)求证:AB∥CD;
(2)若∠3=90°,AE=12cm,AB=5cm,BE=13cm,则AC= cm.
(1)求证:AB∥CD;
(2)若∠3=90°,AE=12cm,AB=5cm,BE=13cm,则AC= cm.
![](https://img.xkw.com/dksih/QBM/2020/7/23/2511862493011968/2512317598056448/STEM/bc093190-83d1-4339-b17e-3684e286c4dc.png?resizew=386)
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【推荐2】如图所示在锐角△ABC中,
,
,AD、BE是三角形的两条高,交于点F,且F是AD中点,G是AB中点,若△AEF绕点F逆时针旋转,旋转角为
(
).
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/5/1d598b08-ef10-4762-aa33-313945fe029f.png?resizew=386)
(1)当
时,请你判断AE与BD的位置关系______;
(2)如图2,当
时,请你直接写出旋转角
(用
表示),以及tan∠ABF的值(用k表示);
(3)在(2)的条件下,连接EG、DG,求EG与DG的数量关系及夹角;
(4)△AEF旋转过程中,是否存在使得△EGD是等腰直角三角形,若存在请你直接写出满足要求的
的值,若不存在请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/148cdaa1d55e9a3d940a4af77610cade.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c36f2598d50b75ae007d0b0f56fd831.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cba48b254cc856ed4f4acb44a8f6eab7.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/5/1d598b08-ef10-4762-aa33-313945fe029f.png?resizew=386)
(1)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6be32a39d99bbd36fff0d12a2708d268.png)
(2)如图2,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4c507610f462120218e2cd1894c957eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
(3)在(2)的条件下,连接EG、DG,求EG与DG的数量关系及夹角;
(4)△AEF旋转过程中,是否存在使得△EGD是等腰直角三角形,若存在请你直接写出满足要求的
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
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【推荐1】已知:点
是平行四边形
对角线
所在直线上的一个动点(点
不与点
、
重合),分别过点
、
向直线
作垂线,垂足分别为点
、
,点
为
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/28/18d1d8bb-d663-4c01-8b08-3568dee475e3.png?resizew=375)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/28/22415e3f-b850-4921-ac4a-fc743ed9e8e1.png?resizew=237)
(1)当点
与点
重合时如图
,易证
(需证明);
(2)直线
绕点
逆时针方向旋转,当
时,如图
、图
的位置,猜想线段
、
、
之间有怎样的数量关系?请写出你对图
、图
的猜想,并选择一种情况给予证明.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/28/18d1d8bb-d663-4c01-8b08-3568dee475e3.png?resizew=375)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/7/28/22415e3f-b850-4921-ac4a-fc743ed9e8e1.png?resizew=237)
(1)当点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dad2a36927223bd70f426ba06aea4b45.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bdaa19de263700a15fcf213d64a8cd57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dcf2e3236ea30ee2c37928b98041f13a.png)
(2)直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2cdba1337ec85fa9722cb4b320a82ae6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b8c1c5ab3096de8b594b59d114268b4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ca7d1107389675d32b56ec097464c14.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a299d2b999568e80be8005565ba209a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ca7d1107389675d32b56ec097464c14.png)
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【推荐2】已知:
中,点E是边
上一点,
交
于点F,
.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/27/33463c5b-c836-43c1-9ae1-4e6a3e3e5922.png?resizew=255)
(1)如图1,当
时,求证:
;
(2)如图2,当
为钝角时,
是否成立?若不成立,请说明理由;若成立,请给出证明.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5138a9f70d5e8b0580e30fef6eb7baef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.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/2dacce99db58d77c25b503db96b59a2e.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/27/33463c5b-c836-43c1-9ae1-4e6a3e3e5922.png?resizew=255)
(1)如图1,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8cfd06965af6014208127f2880b476b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8ab8010e7775d7b5e58935af61d81e8.png)
(2)如图2,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0c543c3ddc3723fde6bbfca3ea3b921b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8ab8010e7775d7b5e58935af61d81e8.png)
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【推荐1】探究与证明
(1)如图1,点B是线段
上的一点,
,
,
,垂足分别为C,B,D,
.求证:
;
类比迁移
(2)如图2,矩形
中,点E、F分别在边
、
上,且
,
,连接
,把三角形
沿
翻叠,若点A的对应点G恰好落在边
上,则
的长为______;
拓展应用
(3)如图3,有一个矩形广场
,
,
,广场上要修两条小路
、
,要求点E、F、G分别在边
、
、
上,且
,
,
,广场上五边形
内部将进行绿化,请求出绿化面积.
(1)如图1,点B是线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/615fc8790237a1b09af51d6bcad6b595.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf4dc4d7d30af1cdce660795e0fd7d7c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5daa413c5a1b941452121c5d750a03e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e3d2d3643a9579f2c693ef86909441e2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0e3e353c4f5fb556b4609a18a903d3d.png)
类比迁移
(2)如图2,矩形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/86338536656046e93b53672ade9a78b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0fc232acd89fc499de346969ce8ced1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b03428a8f91a5674cb8f54766c165f7e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
拓展应用
(3)如图3,有一个矩形广场
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15f325403cbedaac249c9a78d33da81a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0a44328f6afdcc885f0cc21247c1e09.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31e55e398e8520d8a36fb5a625a085b8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.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/aa069231aabec84b0e420a6636b2a78e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/43dad1f58af0e8cb85dd1bfa7df597b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59e6ef4354cf6337fad1b719ff2bf8b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/628bd75a56f7177b03fb21c4ab1782c2.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/2/23/8c4c3d0d-15b9-46e4-826d-e0378c010f7e.png?resizew=526)
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【推荐2】数学研究课上,老师带领大家探究《折纸中的数学问题》时,出示如图
所示的长方形纸条
,其中
,
.然后在纸条上任意画一条线段
,将纸片沿
折叠,
与
交于点
,得到
.如图
所示:
(1)在图
中,若
,
;(直接写出答案)
【操作探究】
(2)改变折痕
位置,
始终是______三角形,请说明理由;
(3)爱动脑筋的小明在研究
的面积时,发现
边上的高始终是个不变的值.根据这一发现,他很快研究出
的面积最小值为
,此时
的大小可以为______;
【拓展延伸】
(4)小明继续动手操作进行折纸,发现了
面积存在最大值,请你求出这个最大值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e1c9ae241fd78126274c65e17990c88.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/341e8dae00f6b2abc94199ccfd6cf180.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/06ff2e2780c282e8ab8e5e88681e1efc.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e5c62f22d7afc5627fcb86599faa8e1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3533837e3d08c461dea031a44e5424d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf3834d7ec7531f3c3c0ce9b286f7a49.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2e4f9a9fd59ac8fde1cd5e456003e10.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c650fe55b7603f106c53ca2423451c6.png)
(1)在图
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c650fe55b7603f106c53ca2423451c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/235a46f917a962ab23ca558a9a957aa0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/911ecd434abc1fd3f4b48c039357ae33.png)
【操作探究】
(2)改变折痕
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2e4f9a9fd59ac8fde1cd5e456003e10.png)
(3)爱动脑筋的小明在研究
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2e4f9a9fd59ac8fde1cd5e456003e10.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/455d9a05141f0e9afa4fca657d0292aa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94e8acea56a9f17e6ef9bbce1633497f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61128ab996360a038e6e64d82fcba004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d5b69d40b75d582c4b8ffa2369af1d41.png)
【拓展延伸】
(4)小明继续动手操作进行折纸,发现了
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2e4f9a9fd59ac8fde1cd5e456003e10.png)
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