直角三角形的三边长分别为3,
,5,化简并求值:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a2a7add4ebf5c26112e5376e7d4b31b7.png)
更新时间:2020-03-28 19:13:05
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解答题-问答题
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【推荐1】已知三角形的两边长为5和7,第三边的边长a.
(1)求a的取值范围;
(2)若a为整数,当a为何值时,组成的三角形的周长最大,最大值是多少?
(1)求a的取值范围;
(2)若a为整数,当a为何值时,组成的三角形的周长最大,最大值是多少?
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解答题-问答题
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【推荐2】阅读材料:若
,求m、n的值.
解:∵
,∴![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcf72e8aad5b0e809dc97ecb8d28a443.png)
∴
,又∵
,
∴
,∴
.
根据你的观察,探究下面的问题:
(1)已知
,则
_____________,
_____________;
(2)根据以上的方法,试说明:代数式
的值一定是一个正数;
(3)已知
的三边长a、b、c都是正整数,且满足:
,求
的周长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19ab3cd8d4125c4ad18333dff0cce5f5.png)
解:∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/19ab3cd8d4125c4ad18333dff0cce5f5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fcf72e8aad5b0e809dc97ecb8d28a443.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bff387e9ae6c9965df41b2930deb6a52.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3adb108038d8219cdd6caeaffadbc259.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/263fd897c8b2f29a18e937f1d1557079.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c4661ff19d6f49d0e52625b52855d7d.png)
根据你的观察,探究下面的问题:
(1)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9c7d4476c0ec5ffbba49e33399e71734.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ec0618ae3a4fde6d6220010af229b9a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/070d1ea22a92808dad7489438c239629.png)
(2)根据以上的方法,试说明:代数式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54d251e0f2a193efb804356379aa60ca.png)
(3)已知
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6130e64af42c176abe61d7b397c1826.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
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解答题-证明题
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【推荐3】【综合探究】为了进一步探究三角形中线的作用,数学兴趣小组合作交流时,小丽在组内做了如下尝试:如图1,在
中,
是
边上的中线,延长
到
,使
,连接
.
的理由是______.
A.
B.
C.
D. ![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b274851ef76d0a57dd315f97f91eade.png)
(2)【初步应用】如图2,在
中,若
,
,求得
的取值范围是______.
A.
B.
C.
D. ![](https://staticzujuan.xkw.com/quesimg/Upload/formula/142869a7cc5e90b551b38210deff9f0f.png)
【感悟】解题时,条件中若出现“中点”“中线”字样,可以考虑延长中线构造全等三角形,把分散的已知条件和所求证的结论集合到同一个三角形中.
(3)【问题解决】如图3,
是
的中线,
交
于
,交
于
,且
.求证:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/88929f4ba0851730d5f941d426b87548.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/764509115979e9958101808383672ec0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/88929f4ba0851730d5f941d426b87548.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bbcb7dd920a799716b5e5febbe4954d6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f0e65e147b109f2bbfd3a3f502bbc3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e8454c9cb0bc6f224d265a1736a26dda.png)
A.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/358dc5c5d5b24efba154bc508c00a021.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48d7d84e698f6d38fa2be14d36c04988.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2f809884ec9bee16549a949d387f60dd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b274851ef76d0a57dd315f97f91eade.png)
(2)【初步应用】如图2,在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/54275b7e571660d0a9e0370fbfe5050b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1682d306c38087d9e6f7efb9cec596a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/88929f4ba0851730d5f941d426b87548.png)
A.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f863e3893cda99d0a42b469f9b0438cd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e145a085312b8fa4af76b85fd7669413.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab7f502effec463bec4889245c4f09a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/142869a7cc5e90b551b38210deff9f0f.png)
【感悟】解题时,条件中若出现“中点”“中线”字样,可以考虑延长中线构造全等三角形,把分散的已知条件和所求证的结论集合到同一个三角形中.
(3)【问题解决】如图3,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/88929f4ba0851730d5f941d426b87548.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d0213c5787a5a6b38d11bceca5567f67.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1a9c6a736e6eac98a676fa3232db5a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a30f3a8b673cc28bd90c50cf1a35281.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/88929f4ba0851730d5f941d426b87548.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0ed1ec316bc54c37c4286c208f55667.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3767efa8adfb71001ad39df9560cbf6a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a5787c784b686435a2073bdeb836307c.png)
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名校
【推荐1】如图,在平面直角坐标系中,函数
的图象分别交x轴、y轴于A、B两点.过点A的直线交y轴正半轴于点C,且点C为线段OB的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/2/05d183cd-8653-4179-a31c-38301a28f39e.png?resizew=107)
(1)求直线AC的表达式.
(2)平面内是否存在点P,使得四边形ACPB是平行四边形?若存在,请求出点P的坐标.
(3)若点Q为直线AC上的一点,且满足
的面积为30,求点Q的坐标.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fa3cffed0825957e4bd1d238039c69fe.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/10/2/05d183cd-8653-4179-a31c-38301a28f39e.png?resizew=107)
(1)求直线AC的表达式.
(2)平面内是否存在点P,使得四边形ACPB是平行四边形?若存在,请求出点P的坐标.
(3)若点Q为直线AC上的一点,且满足
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b17f20c25bb16153b5f2d25062ed7a7.png)
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【推荐2】已知
是
的直径,
是弦,D为
上异于A,C的一点.
的中点,
,求
和
的大小;
(2)如图②,过点D作
的切线,与
的延长线交于点E,
交
于点F,若
的半径为5,
,求
的长.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b79dd200766db27fb90d6bd1992cf658.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1a9c6a736e6eac98a676fa3232db5a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1a9c6a736e6eac98a676fa3232db5a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b0cd1103a6aa22744b54a0fda34519e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21b28f28ced0531d1df34fcf04c6c67f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4189a0821a0ffab9dc171ecd279ba442.png)
(2)如图②,过点D作
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/764509115979e9958101808383672ec0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9672cc271c7f79973c34a1e179782762.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1a9c6a736e6eac98a676fa3232db5a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d97cdc586744d208b6f69c9813af977.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/07160f14b3b453bebb64cb2bf96dc85a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1a6c6e7c025362c46a64a8956761f08e.png)
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