如图,在四边形ABCD中,点G在BC的延长线上,CE平分∠BCD,CF平分∠GCD,过点D作DE⊥CE于点E,DF⊥CF于点F.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/17/1f1d5e52-fce1-4efa-aecf-087c1b45ab72.png?resizew=202)
(1)求证:四边形DECF是矩形;
(2)添加一个条件 ,使四边形DECF是正方形(不用证明)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/17/1f1d5e52-fce1-4efa-aecf-087c1b45ab72.png?resizew=202)
(1)求证:四边形DECF是矩形;
(2)添加一个条件 ,使四边形DECF是正方形(不用证明)
更新时间:2022-08-16 12:42:35
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【推荐2】如图,已知
,
.
;
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度数.
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(2)若
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解答题-证明题
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适中
(0.65)
【推荐1】如图,
和
相交于点
,
,
,点
分别是
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/5/23/922c522b-2b97-4302-b1fe-07e4ca2e236c.png?resizew=160)
(1)求证:
;
(2)当
时,求证:四边形
是矩形.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/35568bac53416f0eb1c79e7306f4c4b7.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2024/5/23/922c522b-2b97-4302-b1fe-07e4ca2e236c.png?resizew=160)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dcf2e3236ea30ee2c37928b98041f13a.png)
(2)当
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解答题-证明题
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适中
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【推荐2】已知:如图,菱形
,分别延长
,
到点
,
,使得
,
,连接
,
,
,
.
(1)求证:四边形
为矩形;
(2)连接
交
于点
,如果
,
,求
的长.
![](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/6b1bd1adfe4cc6566218f19970c2fd3b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
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(1)求证:四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1507da3daed983c2f355d4caebb66d72.png)
(2)连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1dde8112e8eb968fd042418dd632759e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/32c38dfd14dde969702dff97ef2270f9.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
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【推荐1】如图,在四边形ABCD中,AD∥BC,对角线AC⊥BD,垂足为E,点F是BC延长线上的点,且DF⊥DB.
![](https://img.xkw.com/dksih/QBM/2022/4/21/2962989586202624/2965178772709376/STEM/bb2b03554a1c42ea853477ed18b5288c.png?resizew=138)
(1)求证:AD=CF;
(2)当点C为BF中点时,求证:四边形ABCD是菱形;
(3)在(2)的条件下,当△BDF满足什么条件时,四边形ABCD是正方形?(不必说明理由)
![](https://img.xkw.com/dksih/QBM/2022/4/21/2962989586202624/2965178772709376/STEM/bb2b03554a1c42ea853477ed18b5288c.png?resizew=138)
(1)求证:AD=CF;
(2)当点C为BF中点时,求证:四边形ABCD是菱形;
(3)在(2)的条件下,当△BDF满足什么条件时,四边形ABCD是正方形?(不必说明理由)
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名校
【推荐2】已知:如图,在四边形
中,
,
,点E,F分别是
的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/1/0c726af1-63a3-437f-a889-ff59fd2eb83f.png?resizew=209)
(1)求证:
;
(2)当
与
满足什么数量关系时,四边形
是正方形?请证明.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd5bfb81958326445e365d08edd05165.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c4fd85cff10e8f192cfe0b0a8b2f4996.png)
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![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/1/0c726af1-63a3-437f-a889-ff59fd2eb83f.png?resizew=209)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d99bb3ab66b8884bf23cffe1bddcb33.png)
(2)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
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