课本再现
定理证明
(1)为了证明该定理,小明同学画出了图形(如图①),并写出了“已知”和“求证”,请你完成证明过程.
已知:在
中,对角线
,垂足为O.
求证:
是菱形.
(2)已知:如图②,
,
,点E为
的中点,且
.
求证:四边形
是菱形.
思考 我们知道,菱形的对角线互相垂直,反过来,对角线互相垂直的平行四边形是菱形吗? 可以发现并证明菱形的一个判定定理: 对角线互相垂直的平行四边形是菱形. |
(1)为了证明该定理,小明同学画出了图形(如图①),并写出了“已知”和“求证”,请你完成证明过程.
已知:在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5138a9f70d5e8b0580e30fef6eb7baef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cfc1f76257275ab4b04f9bc913535670.png)
求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5138a9f70d5e8b0580e30fef6eb7baef.png)
(2)已知:如图②,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36c4559d27e3905980d1a4f1856f07de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6095bae4840bfa80f2468f94b2002d7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e444739e269a94733b2b0598b559313.png)
求证:四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/910936ec9fb419d51ce2f5ea817f8401.png)
更新时间:2024-04-23 18:56:11
|
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解答题-作图题
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【推荐1】如图,在
中,
,
是
的一个外角.
实验与操作:根据要求进行尺规作图,并在图中标明相应字母(保留作图痕迹,不写作法)
(1)作
的平分线
;
(2)作线段
的垂直平分线,与
交于点
,与
边交于点
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(3)在(1)和(2)的条件下,若
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的度数.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0faed94a64b2dcfc6801b4fca0f16675.png)
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实验与操作:根据要求进行尺规作图,并在图中标明相应字母(保留作图痕迹,不写作法)
(1)作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/721c75fcd58d3d54260aad0f82e09e37.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
(2)作线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21b1efb5d9072a67be9d5497a783016c.png)
(3)在(1)和(2)的条件下,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee5d273b61cb9fefe41937805246fcd4.png)
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【推荐2】学习过等边三角形,小丽用折纸的方法裁出一个等边三角形.如图,先将正方形纸片对折后展开,折痕为
.点E在线段
上,连接
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上的点H处,连接
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裁剪得到
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即为等边三角形,请给予证明.
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解答题-证明题
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名校
【推荐1】如图,在矩形
中,
、
相交于点O,过点D作
,且使得
,连接
,
.
![](https://img.xkw.com/dksih/QBM/2022/4/15/2958595615653888/2959484696027136/STEM/8d792313-8c79-4cc9-967d-5dc603c99cdb.png?resizew=435)
(1)求证:
;
(2)判断四边形
的形状,并说明理由.
![](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/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca14fa885a9d04f04e0418b49b118241.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bb6047a0228d514ad935f42f5bc881c1.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://img.xkw.com/dksih/QBM/2022/4/15/2958595615653888/2959484696027136/STEM/8d792313-8c79-4cc9-967d-5dc603c99cdb.png?resizew=435)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d7c6aedcf4577fe02088bf2ad10690f0.png)
(2)判断四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/74636a04cade98472922f7525c43531f.png)
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【推荐2】如图,在平行四边形
中,
交于点O,点E,F在
上,
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(1)求证:四边形
是平行四边形;
(2)若
,求证:四边形
是菱形.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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(1)求证:四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8bdae3d30abf70515bdbd45f9d0c380.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c6b0f0cdb98fe345dccfa96b3be72b31.png)
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解答题-证明题
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【推荐1】如图,在菱形
中,
交于点
,点
在
上,
求证:四边形
是菱形.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/989c75a3fd02e4971cab421c88de92f1.png)
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【推荐2】如图所示,O是矩形ABCD的对角线的交点,DE//AC,CE//BD,求证OE⊥DC.
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