在学习平行四边形后,小函进行了拓展性研究.她发现,平行四边形
中,在
边上截
,连接
,作
的角平分线交
于点
,则
.她的解决思路是通过证明两条线段所在的四边形是平行四边形得出结论.请根据她的思路完成以下作图和填空:
用直尺和圆规,在
边上截
,连接
,作
的角平分线
,交
于点
(只保留作图痕迹).
已知:如图,四边形
是平行四边形,
,
平分
,交
于点
.求证:
.
是平行四边形,
∴
,
,
,
∴
______,
∵
平分
,
∴
______,
∴
,
∴![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df1ac3ab8d3ce5e61fd2f89761f80976.png)
∵
,
∴
______,
∴
______,
∴![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d8ce1475f537b4ad21775bfaa16daa0c.png)
∴四边形
是平行四边形(一组对边平行且相等的四边形是平行四边形),
∴
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfa8a9b14da8a472a8855449f1160b84.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/727ad3e630a224303d6d3b8ad5c114ba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7c581dab991aeadf06d972e47673ea8.png)
用直尺和圆规,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfa8a9b14da8a472a8855449f1160b84.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/727ad3e630a224303d6d3b8ad5c114ba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
已知:如图,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d3cd8fbcd9eb594adb8367795d444d8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/727ad3e630a224303d6d3b8ad5c114ba.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7c581dab991aeadf06d972e47673ea8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0fff774b4b0087a6f304ce930d359be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c220eadc312101e2fb89dfe920f7b30d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8d2530e7023b2345c651e8f53629ff1.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee8ec5a6d46df6c070e239ae6d642a54.png)
∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/727ad3e630a224303d6d3b8ad5c114ba.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ee8ec5a6d46df6c070e239ae6d642a54.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60faf66a8aca6cff908cb939b5a4e564.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df1ac3ab8d3ce5e61fd2f89761f80976.png)
∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/95adbf026e5ad4ce6f123e5e0b89da7d.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4f76e37d6e6b182896ccaaa187cfe07.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/189d4911005c20ea6d155bb7a9d28a96.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d8ce1475f537b4ad21775bfaa16daa0c.png)
∴四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/910936ec9fb419d51ce2f5ea817f8401.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7c581dab991aeadf06d972e47673ea8.png)
更新时间:2024-04-07 15:21:42
|
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解答题-作图题
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【推荐1】下面是小明设计的“在已知三角形的一边上取一点,使得这点到这个三角形的另外两边的距离相等”的尺规作图过程:
已知:△ABC.
求作:点D,使得点D在BC边上,且到AB,AC边的距离相等.
作法:如图,
作∠BAC的平分线,交BC于点D.则点D即为所求.
根据小明设计的尺规作图过程,
(1)使用直尺和圆规,补全图形 (保留作图痕迹);
(2)完成下面的证明.
证明:作DE⊥AB于点E,作DF⊥AC于点F,
∵AD平分∠BAC,
∴ = ( ) (填推理的依据) .
已知:△ABC.
![](https://img.xkw.com/dksih/QBM/editorImg/2023/12/6/ea77d6e1-95a7-4af9-ae2d-c94e8ff2f4ba.png?resizew=187)
求作:点D,使得点D在BC边上,且到AB,AC边的距离相等.
作法:如图,
作∠BAC的平分线,交BC于点D.则点D即为所求.
根据小明设计的尺规作图过程,
(1)使用直尺和圆规,补全图形 (保留作图痕迹);
(2)完成下面的证明.
证明:作DE⊥AB于点E,作DF⊥AC于点F,
∵AD平分∠BAC,
∴ = ( ) (填推理的依据) .
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解答题-作图题
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适中
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【推荐2】如图,已知四边形ABCD是平行四边形.
(1)用直尺和圆规作出∠ABC的平分线BE,BE交CD的延长线于点E,交AD于点F;(保留作图痕迹,不写作法)
(2)若AB=2cm,BC=3cm,BE=5cm,求BF的长.
(1)用直尺和圆规作出∠ABC的平分线BE,BE交CD的延长线于点E,交AD于点F;(保留作图痕迹,不写作法)
(2)若AB=2cm,BC=3cm,BE=5cm,求BF的长.
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解答题-证明题
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适中
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【推荐1】如图,在平行四边形
中,点E、F分别在
、
上,且
,
.
![](https://img.xkw.com/dksih/QBM/2022/5/21/2984252437118976/3129853905649664/STEM/a92041fd09b04e21899b99926975e9e8.png?resizew=310)
(1)求证:
.
(2)若
,
,
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的长.
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(1)求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea893175f2cd573d877b05b9b4b2e74b.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b76fae293482ceb020d19bd69e9ba78.png)
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解答题-证明题
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适中
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【推荐2】如图,在四边形
中,
,
,
,E为
边上的任意一点,
,且
交
于点F,某学生在研究这一问题时,发现如下事实:
①当
时,有
;
②当
时,有
;
③当
时,有
.
当
时,参照上述研究结论,请你猜想用k表示
的一般结论,并给出证明.
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
①当
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②当
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③当
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当
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