如图,AB=AD,BC=CD,AC与BD相交于点O.
(1)求证:BO=DO;
(2)若AC=4,BD=3,求多边形ABCD的面积.
(1)求证:BO=DO;
(2)若AC=4,BD=3,求多边形ABCD的面积.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/12/18/81686b88-ee6c-48aa-bcfa-4efcf62049d9.png?resizew=139)
更新时间:2021-10-04 09:43:26
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解答题-作图题
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【推荐2】如图所示,网格线交点为格点,
,请用无刻度的直尺在网格中完成下列画图,保留连线的痕迹,不要求说明理由.
![](https://img.xkw.com/dksih/QBM/editorImg/2024/3/26/c874f428-1a9f-494e-aa08-b0f216c4141d.png?resizew=224)
(1)在图1中作
的中线
;
(2)如图1,在
上取点E,使
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(3)在图2中作
的角平分线
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(4)如图2,作格点G,使
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9f08273d339dc5ddbb89aa67bb8205e6.png)
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(1)在图1中作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
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(2)如图1,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f913298f0fae9f55377a8deab9f099dd.png)
(3)在图2中作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
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(4)如图2,作格点G,使
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解答题-问答题
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名校
【推荐3】对于平面内的一个四边形,若存在点
,使得该四边形的一条对角线绕点
旋转一定角度后能与另一条对角线重合,则称该四边形为“可旋四边形”,点
是该四边形的一个“旋点”.例如,在矩形
中,对角线
相交于点
,则点
是矩形
的一个“旋点”.
为“可旋四边形”,其面积是4,则菱形
的边长是______;
(2)如图1,四边形
为“可旋四边形”,边
的中点
是四边形
的一个“旋点”.求
的度数;
(3)如图2,在四边形
中,
,
与
不平行.请问:四边形
是“可旋四边形”吗?若是,请利用尺规作图找出旋转点
,并证明;若不是,也请说明理由.
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(2)如图1,四边形
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(3)如图2,在四边形
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解答题-证明题
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【推荐1】如图,在
中,
,
,D为BC上的一点,连接AD,作
于点E,
交CE的延长线于点F.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/20/5e934899-669e-44c2-8a1c-c99f3ecd32a4.png?resizew=178)
(1)求证:
;
(2)若
,D为BC的中点,求出EF的长.
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(1)求证:
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(2)若
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解答题-证明题
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【推荐2】【数学概念】平移,翻折,旋转是初中数学几何的三大全等变换,无论哪种变换都不会改变图形的形状和大小.
【概念探索】在生活中,我们常用实物体验图形变换的过程.小明同学利用一块四边形纸片完成了如下的操作:
如图1,已知四边形
,
,
.
你认为左右两侧对折后能完全重合吗?如果能,请证明.如果不能,请说明理由.
(2)操作二:对折后,将纸片撕成两个三角形(
和
),先固定
,再将
绕点
顺时针旋转一定的角度(如图3所示)得到
,连接
、
.求证:
.
【应用拓展】(3)如图4,在
中,
,
,点
在边
上,
,点E,F在线段AD上,
,
,若
的面积为
,求
与
的面积之和.
【概念探索】在生活中,我们常用实物体验图形变换的过程.小明同学利用一块四边形纸片完成了如下的操作:
如图1,已知四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
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你认为左右两侧对折后能完全重合吗?如果能,请证明.如果不能,请说明理由.
(2)操作二:对折后,将纸片撕成两个三角形(
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