解题方法
1 . 如图,
中,
,
,
,点D是以BC为直径的半圆弧上的动点,满足
,
.过点D作
交AC于点E,作
交AB于点F.
![](https://img.xkw.com/dksih/QBM/2022/5/9/2975951414378496/2977256452653056/STEM/72a3f6a6-7ed5-41f3-a02f-72ef08c24c92.png?resizew=164)
(1)试用α表示BD的长度;
(2)求
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/15c0dbe3c080c4c4636c64803e5c1f76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/615fc8790237a1b09af51d6bcad6b595.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fc8c65bea2c80af038768b74250c694e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73c916d5b02f278ee842393dab6dcce4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eb278a1476067378944794a3933dfd6f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0ad3351820c5c8f468095c1b93e66c58.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6c0aa4c793921fdaa5d430cb90d78ca6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c5b3f839ce88bf970aceb44ab939bd5b.png)
![](https://img.xkw.com/dksih/QBM/2022/5/9/2975951414378496/2977256452653056/STEM/72a3f6a6-7ed5-41f3-a02f-72ef08c24c92.png?resizew=164)
(1)试用α表示BD的长度;
(2)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/462379369371064bca86df3d386c7c2d.png)
您最近一年使用:0次
2 . 2022年北京冬奥会闭幕式上,呈现了大雪花(火炬)被中国结紧紧包裹的画面,体现了中国“世界大同,天下一家”的理念,数学中也有类似“包裹”的图形.如图,双圆四边形即不仅有内切圆而且有外接圆的四边形,20世纪80年代末,国内许多学者对双圆四边形进行了大量研究,如:边长分别为a,b,c,d的双圆四边形,则其内切圆半径
,外接圆半径
.现有边长均为1的双圆四边形,则![](https://staticzujuan.xkw.com/quesimg/Upload/formula/301e67c1b6864ad87d85ca7237827542.png)
___________ .
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d009ea9ded7f86ab071416d6d551bad4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/80f64d341563df0bded27a366599922d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/301e67c1b6864ad87d85ca7237827542.png)
![](https://img.xkw.com/dksih/QBM/2022/4/21/2962974686560256/2964503704403968/STEM/8a80aa92f49b4e4fbe571cf93f7262fc.png?resizew=151)
您最近一年使用:0次
3 . 如图,
的正方形纸片,剪去对角的两个
的小正方形,然后沿虚线折起,分别粘合AB与AH,ED与EF,CB与CD,GF与GH,得到一几何体Ω,记Ω上的棱AC与EG的夹角为a,则下列说法正确的是___________ .
![](https://img.xkw.com/dksih/QBM/2021/6/6/2736984060076032/2738362151731200/STEM/185bfb1e-a64e-4a53-b3c7-9cc4a20664fb.png)
①几何体Ω中,CG⊥AE;
②几何体Ω是六面体;
③几何体Ω的体积为
;
④
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b0e329a94337ada7c88a4fad9b92f0eb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8d338f176b562d715d5741cf454b9c9.png)
![](https://img.xkw.com/dksih/QBM/2021/6/6/2736984060076032/2738362151731200/STEM/185bfb1e-a64e-4a53-b3c7-9cc4a20664fb.png)
①几何体Ω中,CG⊥AE;
②几何体Ω是六面体;
③几何体Ω的体积为
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf31876698721a199c7c53c6b320aa86.png)
④
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a077ceccea768ed3c664d38d55242fbd.png)
您最近一年使用:0次
2021-06-08更新
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