1 . 下图是小明复习全等三角形时遇到的一个问题并引发的思考,请帮助小明完成以下学习任务.
如图,OC平分
,点P在OC上,M、N分别是
、OB上的点,
,求证:
.
小明的思考:要证明
,只需证明
即可.
证法:如图①:∵OC平分
,∴
,
又∵
,
,∴
,
∴
;
请仔细阅读并完成以下任务:
![](https://img.xkw.com/dksih/QBM/2022/5/3/2971556652843008/2974950110486528/STEM/93b06bfd-3171-47a5-9d77-19e02cb916d0.png?resizew=524)
(1)小明得出
的依据是______(填序号).
①SSS ②SAS ③AAS ④ASA ⑤HL
(2)如图②,在四边形ABCD中,
,
的平分线和
的平分线交于CD边上点P,求证:
.
(3)在(2)的条件下,如图③,若
,
,当△PBC有一个内角是45°时,
的面积是______.
如图,OC平分
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d7b2fe01a33c4825f9974ed9663a99c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef4113c492885ba7c47fe42ac792578f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2032fccdf9ab12429aae024d67b19d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4acd79bb9fb06f7c806eb6e17e4b613.png)
小明的思考:要证明
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4acd79bb9fb06f7c806eb6e17e4b613.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94d54326f92838c51a197cc82985e506.png)
证法:如图①:∵OC平分
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6d7b2fe01a33c4825f9974ed9663a99c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c1f18cef1745d84a0265246684753bd.png)
又∵
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/25ce5cddb3791c46d6ef0c32d35a7886.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2032fccdf9ab12429aae024d67b19d60.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/905a8192e8d6365309562606283e9959.png)
∴
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f4acd79bb9fb06f7c806eb6e17e4b613.png)
请仔细阅读并完成以下任务:
![](https://img.xkw.com/dksih/QBM/2022/5/3/2971556652843008/2974950110486528/STEM/93b06bfd-3171-47a5-9d77-19e02cb916d0.png?resizew=524)
(1)小明得出
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/905a8192e8d6365309562606283e9959.png)
①SSS ②SAS ③AAS ④ASA ⑤HL
(2)如图②,在四边形ABCD中,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/609ada36dd56b33279103ebc1f90bbac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4189a0821a0ffab9dc171ecd279ba442.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d39b8d91afc34e4a9b0fdbb6bafb9087.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6ed66431681da1db8f7cb0f40cd19201.png)
(3)在(2)的条件下,如图③,若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc34db5860990e51ba31edc8cdd077c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/afcd54ff42ebdc70cb273cd5909d549f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/55a675310c8ba418e5a59beb7317e21e.png)
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2 . 为了推导两角和与差的三角函数公式,某同学设计了一种证明方法:在直角梯形ABCD中,
,
,点E为BC上一点,且
,过点D作
于点F,设
,
.
(1)利用图中边长关系
,证明:
;
![](https://img.xkw.com/dksih/QBM/2023/6/20/3263775491006464/3265425842176000/STEM/d80ec35b6b4c44ad9d54317146a5675c.png?resizew=47)
(2)若
,求
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7d8397018b0a01a1b4e9574604f9e76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3f4aca5534bce25acaeb7379deed8f8f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3d5427b7b994b860628df3d6b7a07de8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7aa30a9ee227af2b387cf6e028c20d7d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a447d8fc6919edd758ccec4277435aa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/21461e9cb1265843a16d379788f3fcb8.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/24/b7c91a13-25b3-41d4-9180-c25f2539ec0f.png?resizew=133)
(1)利用图中边长关系
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8904ac51eff2df308ed7b6a07aa2477.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1c8b8ee28cf91c5976d074d233c941f3.png)
![](https://img.xkw.com/dksih/QBM/2023/6/20/3263775491006464/3265425842176000/STEM/d80ec35b6b4c44ad9d54317146a5675c.png?resizew=47)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/952ab659a747b410974aa88748f18d0c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fff423fa9846e49124710a2add054a8f.png)
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解题方法
3 . 如图1,在
中,
,
,点D,E分别在边AB,AC上,
,连接DC,点M,P,N分别为DE,DC,BC的中点.
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/8/d3f9bf69-239d-4a2f-afa6-ab13bae095de.png?resizew=392)
(1)观察猜想:图1中,线段PM与PN的数量关系是________,位置关系是________;
(2)探究证明:把
绕点A逆时针方向旋转到图2的位置,连接MN,BD,CE,判断
的形状,并说明理由;
(3)拓展延伸:把
绕点A在平面内自由旋转,若
,
,请直接写出
面积的最大值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dd967903ed5a6f640a5b801ec8be0070.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f89deb952f57f4b3fa4887b098b7b91.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/047dc9795efa99b6fb9fdf9778085dab.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2d212c1709b8e72a055cf1b5381ef64.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2022/8/8/d3f9bf69-239d-4a2f-afa6-ab13bae095de.png?resizew=392)
(1)观察猜想:图1中,线段PM与PN的数量关系是________,位置关系是________;
(2)探究证明:把
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1ed4c4e8edbd179f3fc38a6653f18c1.png)
(3)拓展延伸:把
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a25c28359f8d8da9eaf4672a6cf8ae4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc11331a7b2d2619b40ee6d34c3bd620.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc34db5860990e51ba31edc8cdd077c2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b1ed4c4e8edbd179f3fc38a6653f18c1.png)
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解题方法
4 . 我国汉代数学家赵爽为了证明勾股定理,创制了一副“勾股圆方图”,后人称其为“赵爽弦图”.类比赵爽弦图,由3个全等的小三角形拼成如图所示的等边
,若
的边长为
﹐且
,则
的面积为___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/619096595112f0340a43b756e114dd3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/61a61d4b2f327fd817c7df7f4fafa02a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/72cb97395ebc5ee1b212afb7a97b985c.png)
![](https://img.xkw.com/dksih/QBM/2021/5/17/2722902761750528/2759990501122048/STEM/bbb8a429-3095-425d-829f-356bc10044b5.png?resizew=197)
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