【问题背景】如图1,P是等边△ABC内一点,∠APB=150°,则PA2+PB2=PC2.小刚为了证明这个结论,将△PAB绕点A逆时针旋转60°,请帮助小刚完成辅助线的作图;
【迁移应用】如图2,D是等边△ABC外一点,E为CD上一点,AD∥BE,∠BEC=120°,求证:△DBE是等边三角形;
【拓展创新】如图3,EF=6,点C为EF的中点,边长为3的等边△ABC绕着点C在平面内旋转一周,直线AE、BF交于点P,M为PG的中点,EF⊥FG于F,FG=4
,请直接写出MC的最小值.
【迁移应用】如图2,D是等边△ABC外一点,E为CD上一点,AD∥BE,∠BEC=120°,求证:△DBE是等边三角形;
【拓展创新】如图3,EF=6,点C为EF的中点,边长为3的等边△ABC绕着点C在平面内旋转一周,直线AE、BF交于点P,M为PG的中点,EF⊥FG于F,FG=4
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a7ffe8515ff6183c1c7775dc6f94bdb8.png)
![](https://img.xkw.com/dksih/QBM/2021/12/23/2878526557978624/2879506624290816/STEM/304057f5-1bba-46de-95fe-2ac09cc994d2.png?resizew=481)
21-22九年级上·湖北武汉·阶段练习 查看更多[2]
湖北省武汉市武汉外国语学校2021-2022学年九年级上学期12月月考数学试题(已下线)24.4(培优课)辅助圆、隐圆(题型精讲精练)-【题型分类精粹】2023-2024学年九年级数学上学期期中期末复习讲练系列【考点闯关】(人教版)
更新时间:2021-12-24 17:14:08
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解题方法
【推荐1】阅读下面材料,完成(1)-(3)题.
数学课上,老师出示了这样一道题:
如图1,已知等腰△ABC中,AB=AC,AD为BC边上的中线,以AB为边向AB左侧作等边△ABE,直线CE与直线AD交于点F.请探究线段EF、AF、DF之间的数量关系,并证明.
同学们经过思考后,交流了自己的想法:
小明:“通过观察和度量,发现∠DFC的度数可以求出来.”
小强:“通过观察和度量,发现线段DF和CF之间存在某种数量关系.”
小伟:“通过作辅助线构造全等三角形,就可以将问题解决.”
......
老师:“若以AB为边向AB右侧作等边△ABE,其它条件均不改变,请在图2中补全图形,探究线段EF、AF、DF三者的数量关系,并证明你的结论.”
![](https://img.xkw.com/dksih/QBM/2020/3/30/2430763817222144/2433649139318784/STEM/25228630fbd64d5c9c5ff9787e631284.png?resizew=191)
![](https://img.xkw.com/dksih/QBM/2020/3/30/2430763817222144/2433649139318784/STEM/7fb3530f018f4cb19cbfe58da449e60b.png?resizew=105)
(1)求∠DFC的度数;
(2)在图1中探究线段EF、AF、CF之间的数量关系,并证明;
(3)在图2中补全图形,探究线段EF、AF、DF之间的数量关系,并证明.
数学课上,老师出示了这样一道题:
如图1,已知等腰△ABC中,AB=AC,AD为BC边上的中线,以AB为边向AB左侧作等边△ABE,直线CE与直线AD交于点F.请探究线段EF、AF、DF之间的数量关系,并证明.
同学们经过思考后,交流了自己的想法:
小明:“通过观察和度量,发现∠DFC的度数可以求出来.”
小强:“通过观察和度量,发现线段DF和CF之间存在某种数量关系.”
小伟:“通过作辅助线构造全等三角形,就可以将问题解决.”
......
老师:“若以AB为边向AB右侧作等边△ABE,其它条件均不改变,请在图2中补全图形,探究线段EF、AF、DF三者的数量关系,并证明你的结论.”
![](https://img.xkw.com/dksih/QBM/2020/3/30/2430763817222144/2433649139318784/STEM/25228630fbd64d5c9c5ff9787e631284.png?resizew=191)
![](https://img.xkw.com/dksih/QBM/2020/3/30/2430763817222144/2433649139318784/STEM/7fb3530f018f4cb19cbfe58da449e60b.png?resizew=105)
(1)求∠DFC的度数;
(2)在图1中探究线段EF、AF、CF之间的数量关系,并证明;
(3)在图2中补全图形,探究线段EF、AF、DF之间的数量关系,并证明.
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【推荐2】如图1,在
中,
,
,将线段
绕点B逆时针旋转
得到线段
.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/18/74a67c1a-ba47-46f6-9d82-be8324fe497e.png?resizew=245)
(1)如图1,直接写出
的大小;(用含
、
的式子表示)
(2)如图2,当
时,E为
外的一点,
,
,判断
的形状,并加以证明.
(3)若将线段
也绕点B顺时针旋转
得到线段
,当C,D,E三点在同一条直线上时,请探究
与
的数量关系,并说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dc9795efa99b6fb9fdf9778085dab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59216f3add27dc502797a3fd69cb9d6b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0e8c9ac0efe45316bd2e028938aa3707.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/1/18/74a67c1a-ba47-46f6-9d82-be8324fe497e.png?resizew=245)
(1)如图1,直接写出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/246a86f34603eaf2e6a948681b831b0d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e170f206fdbbd834aad7580c727e2cc6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
(2)如图2,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b235c077d324c45527cee213a48c1fee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/976fc5c8025c93656b86361dcdfb10a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f2573d44bd027ab2e2fc2472c7852af8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e742966e3711cfa53dce04022acf4bcc.png)
(3)若将线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7dea2ae9d515f9ab351ad72306b776ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3981e7286d41960daf4e110c1c84e03a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b5858ee1ce52b251816757257a11c29.png)
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【推荐3】如图1,已知△ABC为等边三角形,点D,E分别在边AB、AC上, AD=AE ,连接DC,点M,P,N分别为DE,DC,BC的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/18/8b790c10-3fe3-445f-9c22-811857e7347d.png?resizew=355)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/18/68836ba6-441e-46e5-a90e-3ddcc1f41d01.png?resizew=259)
(1)观察猜想
在图1中,线段PM与PN的数量关系是______,∠MPN的度数是______;
(2)探究证明
若△ABC为直角三角形, ∠BAC=90° , AB=AC ,点DE分别在边AB,AC上, AD=AE,把△ADE绕点A在平面内自由旋转,如图2.连接DC,点M,P,N分别为DE,DC,BC的中点.判断△PMN的形状,并说明理由;
(3)拓展延伸
若△ABC中∠BAC=120°, AB=AC=13,点D,E分别在边AB,AC上, AD=AE=5 ,连接DC,点M,P,N分别为DE,DC,BC的中点.把△ADE绕点A在平面内自由旋转,如图3.
①△PMN的是______三角形.
②若△PMN面积为S,直接利用①中的结论,求S的取值取值范围.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/18/8b790c10-3fe3-445f-9c22-811857e7347d.png?resizew=355)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/18/68836ba6-441e-46e5-a90e-3ddcc1f41d01.png?resizew=259)
(1)观察猜想
在图1中,线段PM与PN的数量关系是______,∠MPN的度数是______;
(2)探究证明
若△ABC为直角三角形, ∠BAC=90° , AB=AC ,点DE分别在边AB,AC上, AD=AE,把△ADE绕点A在平面内自由旋转,如图2.连接DC,点M,P,N分别为DE,DC,BC的中点.判断△PMN的形状,并说明理由;
(3)拓展延伸
若△ABC中∠BAC=120°, AB=AC=13,点D,E分别在边AB,AC上, AD=AE=5 ,连接DC,点M,P,N分别为DE,DC,BC的中点.把△ADE绕点A在平面内自由旋转,如图3.
①△PMN的是______三角形.
②若△PMN面积为S,直接利用①中的结论,求S的取值取值范围.
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【推荐1】如图,
是
外接圆,
是
的直径,弦
于点H,
与
相交于点G,
的延长线交于点F,P是
的中点,连接
.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/6/ef0549d2-3286-4508-9ba6-6fd319e3f59d.png?resizew=119)
(1)求证:
是
的切线;
(2)若
的半径是1,
,
,求
的长?
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e428e7a09732be85c1224e9c8f6a71c5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32c38dfd14dde969702dff97ef2270f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b194d0da4190a51a7aa4b6391f511cc3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0e57a13c665af88f326c9890072bf73.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/6/ef0549d2-3286-4508-9ba6-6fd319e3f59d.png?resizew=119)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48f3c9abbd78e9a6840ee5f30381daac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3682339774bf9b7cc1410f9fa07d4e60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c42ed2e5bd5a0f033e24008697bf4963.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c4cd68cc82e90a5e2049a7ea3171b84.png)
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【推荐2】如图1,O为圆的圆心,C,D为圆上的两点,且
,连接AC并延长,与BD的延长线相交于点E.
![](https://img.xkw.com/dksih/QBM/2022/5/7/2974403286876160/2976278883508224/STEM/e588247a-b447-499a-830e-cb11c9e11174.png?resizew=232)
(1)求证:
;
(2)如图2,连接OC,BC,AD.AD与OC,BC分别交于点F,H.若圆的直径为10,
,请直接写出AC的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/532aece6cfd67e2a97977eed978dbf2b.png)
![](https://img.xkw.com/dksih/QBM/2022/5/7/2974403286876160/2976278883508224/STEM/e588247a-b447-499a-830e-cb11c9e11174.png?resizew=232)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5f21678a0009eb39b6886653d295b09a.png)
(2)如图2,连接OC,BC,AD.AD与OC,BC分别交于点F,H.若圆的直径为10,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32f01c4faacedfe56f5127d6c0cc63cf.png)
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【推荐1】阅读下列材料:
已知实数m,n满足
,试求
的值.
解:设
,则原方程变为
,整理得
,
,所以
,因为
,所以
,上面这种方法称为“换元法”,把其中某些部分看成一个整体,并用新字母代替(即换元),则能使复杂的问题简单化.根据以上阅读材料内容,解决下列问题,并写出解答过程.
(1)已知实数x、y满足
,求
值;
(2)已知
的三边为a、b、c(c为斜边),且a、b满足
,
外接圆的半径.
已知实数m,n满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4f63e7889194dd388eed961b224bde78.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/279847760a3af31532efd4dc6969092b.png)
解:设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7a20d6cce46fdb238eff15570752ce50.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fee5aa4961b705d28fe350062108dd8d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6004bbb28b182cb0695010ed88f1e6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7bc930dd1ddc515cbb27cff06a8b35c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0ab364036827e64dcb23a25c7e5784ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9bed5e7d3421bfaace2a1bf6d62319ea.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a788b6a5da7f7c8f1d7d8f8a620564c.png)
(1)已知实数x、y满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8498925525c43833f19baa5169d45a41.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/29ebc856291255f2d4a6c20b982a2442.png)
(2)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aefc12c61c95d8e36846a6aac1c9105b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a011d6594c68454bf7e8c4fc101eb71f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d36d87153e50e195347e7b7ef685a462.png)
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【推荐2】如图,平面直角坐标系中有4个点:A(0,2),B(﹣2,﹣2),C(﹣2,2),D(3,3).
(1)在正方形网格中画出△ABC的外接圆⊙M,圆心M的坐标是 ;
(2)若EF是⊙M的一条长为4的弦,点G为弦EF的中点,求DG的最大值;
(3)点P在直线MB上,若⊙M上存在一点Q,使得P、Q两点间距离小于1,直接写出点P横坐标的取值范围.
(1)在正方形网格中画出△ABC的外接圆⊙M,圆心M的坐标是 ;
(2)若EF是⊙M的一条长为4的弦,点G为弦EF的中点,求DG的最大值;
(3)点P在直线MB上,若⊙M上存在一点Q,使得P、Q两点间距离小于1,直接写出点P横坐标的取值范围.
![](https://img.xkw.com/dksih/QBM/2018/5/24/1952489105489920/2009096497078272/STEM/de3379cf918c4b0799c9b575a25b774b.png?resizew=212)
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名校
【推荐3】问题提出
(1)如图1,在
中,点D在BC上,连接AD,
,则
与
的面积之比为______;
问题探究
(2)如图2,在矩形ABCD中,
,
,点P为矩形内一动点,在点P运动的过程中始终有
,求
面积的最大值;(结果保留根号)
问题解决
(3)如图3,某市欲规划一块形如平行四边形ABCD的休闲旅游观光区,点A为观光区的入口,并满足
,要求在边BC上确定一点E为观光区的南门,为了方便市民游览,修建一条观光通道AE(观光通道的宽度不计),且
,
米,为了容纳尽可能多的游客,要求平行四边形ABCD的面积最大,请问是否存在满足上述条件的面积最大的平行四边形ABCD?若存在,求出平行四边形ABCD的最大面积;若不存在,请说明理由.(结果保留根号)
(1)如图1,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f8cabcef1cee1213140371c499339864.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab2a2834d80ff574e79eae8ca8d4e94f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7ac451db3443cabb204f96c31fd4a02e.png)
问题探究
(2)如图2,在矩形ABCD中,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d2c15801fee2405573677484f5dcfa4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07140f277a35733d8c97577ccdd4e3ab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a6901e8b018a80e917540462d2f3aadd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/af2cc5f8cec8c498aa12c99c04e1c97d.png)
问题解决
(3)如图3,某市欲规划一块形如平行四边形ABCD的休闲旅游观光区,点A为观光区的入口,并满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9eee296a7d9fba487f1485c61580196f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a55c3f663b6b205bb0d541a72e4d4759.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ee2dac77daebb25f50647abc3249200.png)
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解答题-证明题
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较难
(0.4)
【推荐1】在Rt△ABC中,
,D,E,F分别是边AB,AC,BC上的点,
,
.
![](https://img.xkw.com/dksih/QBM/2022/5/25/2987113735004160/2989005124173824/STEM/b978b338-4c70-4e4a-bb11-ea907a4c004c.png?resizew=536)
(1)如图1,若
,
,直接写出
的值;
(2)如图2,若
,
,(1)中的结论是否仍然成立?请证明你的结论;
(3)如图3,若
.
①求tan∠DFE的值;
②直接写出
的值.(用含n的代数式表示)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08f77256d3db06fe922ef699df09a3b7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b91f064bb73019053992fe781a53356a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/602ef38dc96e6e186a0a22cfd511bf5d.png)
![](https://img.xkw.com/dksih/QBM/2022/5/25/2987113735004160/2989005124173824/STEM/b978b338-4c70-4e4a-bb11-ea907a4c004c.png?resizew=536)
(1)如图1,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7099026716ee1821dd7d9f157dc055f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c87b351f16728b0023fd63678f8103c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b2817671406f99b937023ed3d54f173.png)
(2)如图2,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df92b77039c6c22396a5e85877bc038a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c87b351f16728b0023fd63678f8103c7.png)
(3)如图3,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7099026716ee1821dd7d9f157dc055f5.png)
①求tan∠DFE的值;
②直接写出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3eb33ce523fa361a6cc63204af835317.png)
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较难
(0.4)
真题
名校
【推荐2】如图,在平面直角坐标系中,已知抛物线
的顶点为A,与y轴交于点C,线段
轴,交该抛物线于另一点B.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/29/c7ed9d35-e501-4456-b5a9-c562281d5370.png?resizew=430)
(1)求点B的坐标及直线
的解析式:
(2)当二次函数
的自变量x满足
时,此函数的最大值为p,最小值为q,且
.求m的值:
(3)平移抛物线
,使其顶点始终在直线
上移动,当平移后的抛物线与射线BA只有一个公共点时,设此时抛物线的顶点的横坐标为n,请直接写出n的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17d794141572c8b1e70957754f32b9eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81bc6135fa3da5b1c291e9231ebe5b8a.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/6/29/c7ed9d35-e501-4456-b5a9-c562281d5370.png?resizew=430)
(1)求点B的坐标及直线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
(2)当二次函数
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17d794141572c8b1e70957754f32b9eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b7b9d1aed28257832e95e5cd02a40b26.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9ec7849499a43c790d8150c29a5ed34a.png)
(3)平移抛物线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/17d794141572c8b1e70957754f32b9eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
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解答题-证明题
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较难
(0.4)
【推荐3】某数学兴趣小组在数学课外活动中,对多边形内两条互相垂直的线段做了如下探究:
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/24/9dd7adef-d4d2-451e-b0e9-a34f4b5b8f89.png?resizew=544)
【观察与猜想】
(1)如图1,在正方形
中,点
,
分别是
,
上的两点,连接
,
,
,则
的值为___________;
(2)如图2,在矩形
中,
,点
是
上的一点,连接
,
,且
,则
的值为___________;
【类比探究】
(3)如图3,在四边形
中,
,点
为
上一点,连接
,过点
作
的垂线交
的延长线于点
,交
的延长线于点
,求证:
;
【拓展延伸】
(4)如图4,在
中,
,
,
,将
沿
翻折,点
落在点
处得
,点
,
分别在边
,
上,连接
,
,且
,求
的值.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/2/24/9dd7adef-d4d2-451e-b0e9-a34f4b5b8f89.png?resizew=544)
【观察与猜想】
(1)如图1,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/a0ed1ec316bc54c37c4286c208f55667.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/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f87b02b744534ae1ed700d21fcceb4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9ada5e380d6b5b2066e34497e5f0baf0.png)
(2)如图2,在矩形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1983c41ebdacc818687e43642f8fb670.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/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a45b04cc3e5adaeff6f9e01e29032803.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8775dcf60ad143bc59a58b000f374c56.png)
【类比探究】
(3)如图3,在四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/41aba1711910c6f533cc94319104f4fd.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/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21037e170bdbb322558e79c40c00b454.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.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/ccb545c1a90c841d0d25070cf62b64e3.png)
【拓展延伸】
(4)如图4,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13ab0e3f4783faa57520f1f9dff63439.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce0d7095ddd69d6ceaf1065b1bc2c79d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d2c15801fee2405573677484f5dcfa4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04ee826937d2add7a93aaa1422f8b736.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab2a2834d80ff574e79eae8ca8d4e94f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.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/73636989e83905f8800a865c2b608c43.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/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d1f87b02b744534ae1ed700d21fcceb4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9ada5e380d6b5b2066e34497e5f0baf0.png)
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