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.
已知: ,求证: .
证明: .
(2)如图2,在平行四边形
中,对角线
和
相交于点O,
,
,
.求证:平行四边形
是菱形.
已知: ,求证: .
证明: .
(2)如图2,在平行四边形
![](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/ecf7679c8b4b1e442ce4286d4b0e9c32.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4494a85de0be0b97a69348115aef8513.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/454328a8e75953fdb0835ce80d9566e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
更新时间:2024-05-26 16:27:32
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名校
【推荐2】如图,已知等腰
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【推荐1】如图,在
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解答题-证明题
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【推荐2】在
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(1)如图1,求证:四边形
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(2)如图2,若
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解答题-作图题
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适中
(0.65)
【推荐1】如图,已知四边形
是平行四边形.
,分别交
、
于点
、
(不写作法,保留作图痕迹);
(2)在(1)的条件下,若
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,求菱形
的面积.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a02b1139e07e431b5d4276757b232bad.png)
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(2)在(1)的条件下,若
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解答题-证明题
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适中
(0.65)
【推荐2】(1)如图①,在平行四边形ABCD中,AC、BD交于点O,过点O作直线EF分别交AD、BC于点E、F,![](https://img.xkw.com/dksih/QBM/2016/9/7/1574231863238656/1574231869538304/STEM/50f3d6b8373f496e98b10db38a59c0c7.png)
求证:OE=OF.
(2)在图①中,过点O作直线GH分别交AB、CD于点G、H,且满足GH⊥EF,连结EG、GF、FH、HE.如图②,试判断四边形EGFH的形状,并说明理由;
(3)在(2)的条件下,
若平行四边形ABCD变为矩形时,四边形EGFH是 ;
若平行四边形ABCD变为菱形时,四边形EGFH是 ;
若平行四边形ABCD变为正方形时,四边形EGFH是 .
![](https://img.xkw.com/dksih/QBM/2016/9/7/1574231863238656/1574231869538304/STEM/50f3d6b8373f496e98b10db38a59c0c7.png)
求证:OE=OF.
(2)在图①中,过点O作直线GH分别交AB、CD于点G、H,且满足GH⊥EF,连结EG、GF、FH、HE.如图②,试判断四边形EGFH的形状,并说明理由;
(3)在(2)的条件下,
若平行四边形ABCD变为矩形时,四边形EGFH是 ;
若平行四边形ABCD变为菱形时,四边形EGFH是 ;
若平行四边形ABCD变为正方形时,四边形EGFH是 .
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