1 . 如图,在矩形
中,
,
,P是边
上的任意一点,连接
,
,E,F,G分别是
,
,
的中点.
与
的数量关系为________;位置关系为________;
(2)试猜想:当点P位于什么位置时,四边形
是菱形?并证明猜想的正确性;
(3)若(2)中菱形
为正方形,直接写出a与b之间的数量关系.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d42e97eee705d164e6ac6de9ecd6d1f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c52b857c7ca55dfa6da108df1d3cee2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e52a8f07834cbbbe4224962672fbbb2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d2be49c37e30a3ced0364c3e74d8c687.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2cdba1337ec85fa9722cb4b320a82ae6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bd33764ff4efddfe11a98a609753715c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4505508b3e36db64a207dcdaf8eb22dc.png)
(2)试猜想:当点P位于什么位置时,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0363419eabe432409a7f04598450a396.png)
(3)若(2)中菱形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0363419eabe432409a7f04598450a396.png)
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2 . 综合与实践
问题背景:三角形的中位线定理是人教版初中数学八下教材的一个重要命题.
如图1,
是
的中位线.则
,且
.
(1)如图1,若
,则
________;
(2)回顾证法:
证明三角形中位线定理的方法很多,但多数都要通过添加辅助线构图完成.图2是其中一种辅助线的添加方法(“倍长中线”法).
请结合图2,完成“三角形中位线定理”的证明过程;
中,点
,
分别是
,
的中点.
求证:
,且
.
(3)方法迁移:
如图3,四边形
和
均为正方形,连接
,
,
是
的中点,连接
,已知线段
.请求出线段
的长.
问题背景:三角形的中位线定理是人教版初中数学八下教材的一个重要命题.
如图1,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c436f108fd4921dae15ecff19270237e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/950e82a0f9712457f2dd9f8a93f8a217.png)
(1)如图1,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aa7aeb2a8d1437eeb4482c3b6ad9f315.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/404728d0ea2699c71e674f30dd984abd.png)
(2)回顾证法:
证明三角形中位线定理的方法很多,但多数都要通过添加辅助线构图完成.图2是其中一种辅助线的添加方法(“倍长中线”法).
请结合图2,完成“三角形中位线定理”的证明过程;
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c436f108fd4921dae15ecff19270237e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/950e82a0f9712457f2dd9f8a93f8a217.png)
(3)方法迁移:
如图3,四边形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2257da1e2425f2ea9ac7440f52659ff.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/77a7e4a6765ce78b05ee97764771e01f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/77a7e4a6765ce78b05ee97764771e01f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b3533837e3d08c461dea031a44e5424d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87b6497c7cada9c849f92d9ad00547ef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
您最近一年使用:0次
3 . 从4 地出发前往B地由于被一座山隔开而导致公路无法直达,需绕道C地,这大大影响了A、B两地居民的日常生活,现在国家决定投资从A地修建一条隧道(如图中虚线所示)穿过山直达 B地. 现在测得公路
长42千米,
长50千米,
的中点 D、
的中点E 之间距离
长20千米.A、B间直达公路通车后,通行距离将比原来绕道 C 地缩短了_______ 千米.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b1bd1adfe4cc6566218f19970c2fd3b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b1bd1adfe4cc6566218f19970c2fd3b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
您最近一年使用:0次
2024-06-02更新
|
60次组卷
|
3卷引用:河南省洛阳市西工区2023-2024学年八年级下学期期中数学试题
河南省洛阳市西工区2023-2024学年八年级下学期期中数学试题河南省洛阳市洛龙区2023-2024学年八年级下学期期中数学试题(已下线)专题6.7 三角形的中位线(分层练习)-2023-2024学年八年级数学下册基础知识专项突破讲与练(北师大版)
4 . 证明:三角形的三条中线交于一点.
已知:如图,
、
是
的中线,
、
交于点O,连接
并延长交
于点F.
求证:
是
的中线.
小明进行了以下思考,证明:延长
至点G,使得
,连接
、
…
(请沿着小明的思考,将证明过程补充完整.)
已知:如图,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/aaf1438142deeac876fc7dc50552e552.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/274cf35acb4a1748d15c39d15a9bea7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
小明进行了以下思考,证明:延长
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/274cf35acb4a1748d15c39d15a9bea7b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cd011326209a8899b72489c75f7316be.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/77a7e4a6765ce78b05ee97764771e01f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/abf80148409afb32ced0b4f59f1ba709.png)
(请沿着小明的思考,将证明过程补充完整.)
您最近一年使用:0次
5 . 如图,平行四边形
的顶点
在等腰直角三角形
的边
上,点
在
的延长线上,
为
的中点,连接
,若
,
,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96cf3f9a01a810792ebacc7f5bc70e97.png)
_________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f84f169e50dc59d4f7a8e1e36f5c847.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7bef5239ddbb0972700ce01daf9ee7cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6b1bd1adfe4cc6566218f19970c2fd3b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fc56c77464a17a1e97b568762a3e2c6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c63e36329f5e0979f5ee776ac5d06327.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ea147ada4f0aefdd3808a6a1133792eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a129e278b34ae1a844528cbf7315a872.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96cf3f9a01a810792ebacc7f5bc70e97.png)
您最近一年使用:0次
6 . 阅读下面的内容:
求证:三角形的中位线平行第三边且等于第三边的一半.
已知:
中
、
分别是
、
的中点.
求证:
,且
.
证明:过点
作
的平行线交
的延长线于点
,如图所示:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fb85f16ecc7e3766ae31816473eadb8.png)
,
,
,
又
,
,
,
,
,
,
又![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fb85f16ecc7e3766ae31816473eadb8.png)
,
四边形
是平行四边形,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c7732cf10195a6b81c141b609fafb35.png)
,且
,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6911a6519903fb7e464ab74e873996a4.png)
,且
.
类似的,连接梯形两腰中点的线段叫梯形的中位线.
如图,梯形
中
,
、
分别是腰
、
的中点,
就是梯形中位线.
梯形的中位线性质:梯形的中位线平行于两底并且等于两底和的一半.
请参考例题证明梯形的中位线性质.
已知:如图梯形
中
,
、
分别是腰
、
的中点.
求证:________________.
证明:_____________________.
求证:三角形的中位线平行第三边且等于第三边的一半.
已知:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8455657dde27aabe6adb7b188e031c11.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
求证:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c436f108fd4921dae15ecff19270237e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/950e82a0f9712457f2dd9f8a93f8a217.png)
证明:过点
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fb85f16ecc7e3766ae31816473eadb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13a83e7ca69f682b0a94683ab914393c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dd2de6aa992cbba77e27b398d3b1b3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/badde435cf8beb6b0144e87f4daa33d2.png)
又
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/23f7d76e89d47c1a625022283449c8d6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/593887bde48a67b752342911a6c70713.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d75c5a0c9649fcb47337b73373381eab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/757eb5a16a8ede8ea439fd5cbb533004.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/846cf2133db64063fc696fdca8334426.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/38303a9f59e6c79c99a2ee2761f04ce9.png)
又
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1fb85f16ecc7e3766ae31816473eadb8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/784644336f2417214eeace1592223b31.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2de0d10ef8b748d4531250c37c5d3f9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1cf2fa3cb87267ee5f968c2a9362d216.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c7732cf10195a6b81c141b609fafb35.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f68f4424008113481d68afd2ca5172e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b045477e04ff80c3b8f962e134aa0959.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6911a6519903fb7e464ab74e873996a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f68f4424008113481d68afd2ca5172e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/950e82a0f9712457f2dd9f8a93f8a217.png)
类似的,连接梯形两腰中点的线段叫梯形的中位线.
如图,梯形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4adf90a8c2b29334cdc5aa5b554991f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
梯形的中位线性质:梯形的中位线平行于两底并且等于两底和的一半.
请参考例题证明梯形的中位线性质.
已知:如图梯形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4adf90a8c2b29334cdc5aa5b554991f9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9d78abbad68bbbf12af10cd40ef4c353.png)
求证:________________.
证明:_____________________.
您最近一年使用:0次
7 . 已知:点
在正方形
的边
的延长线上,连接
,过点
作
,交边
于点
.
与
的数量关系,并说明理由:
(2)如图2,连接
,
,作
的平分线交
于点
,求证:
;
(3)如图3,在(2)的条件下,连接
,过点
作
,交
的延长线于点
,
为
的中点,连接
.若
,
,请求出
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.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/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5db41a1f31d6baee7c69990811edb9f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cbfc332950d19764830174dba000b9bd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
(2)如图2,连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/49b50357a6545cae8348e3059312f520.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/13a2e6494cf8d2dff0746a9bb72cef43.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/895dc3dc3a6606ff487a4c4863e18509.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fd0a09c7f9a71ae398f6abfe745d0ac7.png)
(3)如图3,在(2)的条件下,连接
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31e55e398e8520d8a36fb5a625a085b8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d46ff5ad25f193b77c7faa997867cc1c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/31e55e398e8520d8a36fb5a625a085b8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54a5d7d3b6b63fe5c24c3907b7a8eaa3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6aa2b5e09f8ec785c59900a529390a02.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/495be6a6b940e8affe38f2bcdee246b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/87b85d7d422571c4cc3aa5e09505fd67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
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名校
8 . 小凡同学在学习了三角形中位线定理后,重新组合题设和结论,得到如下命题:在三角形内,经过三角形一边的中点,且与另一边平行的线段,是三角形的中位线.即在
中,若D为
中点,
,则E为
中点.
(1)请你完成这一命题的证明.
(2)小凡同学发现由这个命题可以得到一种作线段中点的方法:
如图,要作线段
的中点:
①作射线
;
②以A为圆心,适当长为半径画弧,交射线
于点E,再以E为圆心,以
长为半径画弧,交射线
于点C;
③连接BC,过点E作
交
于点D,连接
,则点D为线段
的中点.
五等分(不必证明,保留作图痕迹,平行线可通过三角尺、直尺完成,无需尺规作图).
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1d021981c03e75b1a246d899dcc64656.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
(1)请你完成这一命题的证明.
(2)小凡同学发现由这个命题可以得到一种作线段中点的方法:
如图,要作线段
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
①作射线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
②以A为圆心,适当长为半径画弧,交射线
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/68a83fdd2ba72a2dba0b6b10bb3e06b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d50703c46b6153945d718b198f03b4b5.png)
③连接BC,过点E作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1d021981c03e75b1a246d899dcc64656.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a6c6e7c025362c46a64a8956761f08e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
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9 . 我们学习了三角形中位线定理:三角形中位线平行于第三边并且等于第三边的一半.
在
中,D、E分别是
、
的中点. 通过延长
至F,使
,连接
,易证:
且
.
如果将
截去,剩下梯形
且
,取
、
的中点M、N,连接
,则
叫梯形
的中位线,探索
与
和
的关系. 写出结论 ,请证明你的结论;
在梯形
中,
,
,
,M、N分别是
、
的中点,
,求梯形
的面积.
在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f52a58fbaf4fea03567e88a9f0f6e37e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60ef95894ceebaf236170e8832dcf7e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21c834a2ede139af87f2d1516b476a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4cae70b8a9d2d2e96dea62c00ced04b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c436f108fd4921dae15ecff19270237e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/950e82a0f9712457f2dd9f8a93f8a217.png)
如果将
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65c42bce098904b241986bb91c65ab33.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c436f108fd4921dae15ecff19270237e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65c42bce098904b241986bb91c65ab33.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411461db15ee8086332c531e086c40c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e6e490f703eb6c9bb1278c78ebc2d661.png)
在梯形
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65c42bce098904b241986bb91c65ab33.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c436f108fd4921dae15ecff19270237e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/56d3c9ce32b721995f355eea411340e3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1337ce85d29edabcc2fadb9a9cc31ce5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d40b319212a7e7528b053e1c7097e966.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4eedae8d316c76e3d0b451256de03fb9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/696009de37774e06bf28631f79fb60d8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/65c42bce098904b241986bb91c65ab33.png)
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10 . 平行四边形
中,点E在
上方,
交
于点F,连接
交
于点G,
,![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9e7d6f02cc530a960a28e00ce2a8898.png)
(2)如图2,连接AE,若
求证:![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be5fc6ead6416492c231c320a5486f86.png)
(3)如图3,在(2)的条件下,过点E作
交
的延长线于点H,作
交
于点K.若
,
,求线段
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/411b38a18046fea8e9fab1f9f9b80a5f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d25f8eb66299a0f6650c331d4f50d47d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/85c4bdfb0db1e31e8459df1d15f9ab55.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/03902478df1a55bc99703210bccab910.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f30f7e609b27a56d8b68f4d0bfc50759.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a9e7d6f02cc530a960a28e00ce2a8898.png)
(2)如图2,连接AE,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/701b71021fa4753304885b6e5e39b99d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/be5fc6ead6416492c231c320a5486f86.png)
(3)如图3,在(2)的条件下,过点E作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/812c74f78fb32ab99ac41f742f1fe2de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7dea2ae9d515f9ab351ad72306b776ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f3684b60071ad4fcf7631ad9803f4856.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/826c728050e3378921442ace20269ef6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/500da6c55f25483978465eb5e99ab8d5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a064c99f1def2a6adb2fc26e8e5b0272.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0dc5c9827dfd0be5a9c85962d6ccbfb1.png)
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