如图,在平行四边形ABCD中,点E为BC的中点,AE与对角线BD交于点F.
(1)求证:DF=2BF;
(2)当∠AFB=90°且tan∠ABD=
时, 若CD=
,求AD长.
(1)求证:DF=2BF;
(2)当∠AFB=90°且tan∠ABD=
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2967337e3fcb228dded64ab0c41a17e0.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/11/30/a4a28bc1-eff2-4c58-a109-ae97e06cc0ed.png?resizew=220)
更新时间:2017-05-25 15:45:57
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【知识点】 添一个条件成为平行四边形解读
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解答题-作图题
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适中
(0.65)
名校
【推荐1】小云学习了平行四边形的判定后,想利用平行四边形的判定方法探究下列问题.
![](https://img.xkw.com/dksih/QBM/2022/4/27/2967089173970944/2970809180635136/STEM/2d944147-1574-494b-b595-cc9b039ef285.png?resizew=553)
(1)利用平行四边形的判定方法作平行四边形,作法是:如图1,在
中,分别以点A,C为圆心,
为半径画弧,两弧交于点D,连接
,四边形
就是平行四边形.小云判定四边形
平行四边形的依据是___________;
(2)探究:“四边形
中,若
,对角线
与
交于点O,且
,四边形
是平行四边形吗?”
①在图2中作出符合条件的图形(尺规作图,保留作图痕迹);
②结合所作图形,符合条件的四边形
________(填写“是”、“不是”或“不一定是”)平行四边形.
(3)探究:“四边形
中,若
,对角线
与
交于点O,且
,
,当
与
满足什么条件时,四边形
一定是平行四边形?”直接写出
与
满足的条件是: ____________.
![](https://img.xkw.com/dksih/QBM/2022/4/27/2967089173970944/2970809180635136/STEM/2d944147-1574-494b-b595-cc9b039ef285.png?resizew=553)
(1)利用平行四边形的判定方法作平行四边形,作法是:如图1,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd6877751384616819a8ddeef96c4133.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e7835c72d14f9d61b95b15aa47fafac2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(2)探究:“四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c220eadc312101e2fb89dfe920f7b30d.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/0944865f14b13a772526c4cae4f29c99.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
①在图2中作出符合条件的图形(尺规作图,保留作图痕迹);
②结合所作图形,符合条件的四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
(3)探究:“四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c220eadc312101e2fb89dfe920f7b30d.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/0944865f14b13a772526c4cae4f29c99.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5784ea22dbd90af6cdceae43f80a22e8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2c3d2cba96f6f03520c0b3f6e4da03e.png)
![](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/e2c3d2cba96f6f03520c0b3f6e4da03e.png)
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解答题-证明题
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适中
(0.65)
【推荐2】如图,在
中,
,
,
,点
、
分别是边
、
上的动点(点
不与
,
重合),且
,过点
作
的平行线
,交
于点
,连接
,设
为
.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/8/fa032e4e-8bfc-42e2-a89f-a9d39a0da519.png?resizew=173)
(1)求证:
∽
.
(2)是否存在一点
,使得四边形
为平行四边形,若存在,请求出
的值;若不存在,请说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f89deb952f57f4b3fa4887b098b7b91.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/efc6e4b936d7a800e839a30c3839574d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8a7b5adfcac0f46a4cd19da4ebb4a2b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/514191a070dc6951f7d65d251602b3b4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3171b3d11c6f4619e189677345357508.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cb6ede9761b5b90f8dc137708e1ee90f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/3/8/fa032e4e-8bfc-42e2-a89f-a9d39a0da519.png?resizew=173)
(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd151311cabece2c170115ef455986c0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
(2)是否存在一点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/acc290b44635265137fdf13146b6a6d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4d907d0421af03d1a5daf017d71f371c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81dea63b8ce3e51adf66cf7b9982a248.png)
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