题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161020-93860.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161020-79916.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161021-46851.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161021-90497.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161021-38600.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161021-30835.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161022-97903.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161022-96494.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161022-51346.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161022-84957.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161023-46765.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161023-70498.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161023-82593.png)
解:∵∠ACB=90°,∠CAB=30°,BC=2,
∴AB=2BC=4,
∴AC=
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161024-18749.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161024-66710.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161024-24520.png)
∵O、H分别为AB、AC的中点,
∴OB=
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161024-40993.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161024-40993.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161024-24520.png)
在Rt△BCH中,BH=
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161024-67345.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161025-24780.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161025-48694.png)
∵旋转角度为120°,
∴阴影部分的面积=
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161025-61253.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161025-82783.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161026-21121.png)
故答案为:
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161023-70498.png)
本题考查了扇形的面积计算,直角三角形的性质,旋转变换的性质,观察出阴影部分的面积的表示是解题的关键.
核心考点
举一反三
O(0,0),
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161015-20056.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161015-35908.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161015-20056.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161015-35908.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161016-63415.png)
(1)在所给的平面直角坐标系xOy中画出旋转后的
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161016-64357.png)
(2)求点B旋转到点
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161016-68874.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161016-88426.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161012-24475.png)
⑴试判断图乙中△ODE和△OCF是否全等,并证明你的结论.
⑵若正方形ABCD的对角线长为10,试求三角板和正方形重合部分的面积.
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161004-99398.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161004-46891.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161005-40115.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161004-99398.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161005-78597.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161005-87651.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161005-46672.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161006-59395.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161006-39443.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161006-36440.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161006-73356.png)
A.1 | B.2 | C.3 | D.4 |
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106160959-56018.png)
(1)请你画出此图案绕点O顺时针方向旋转90°,180°,270°的图案,你会得到一个美丽的图案,千万不要将阴影位置涂错;
(2)若网格中每个小正方形的边长为1,旋转后点
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106160959-46933.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106160959-21444.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106160959-17980.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106160959-83264.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191106/20191106161000-78392.png)
(3)这个美丽图案能够证明一个我们学过的著名定理,请直接写出这个定理名称,不要求证明。
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