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在Rt△ABC中,∠C=90°,BC=4cm,AC=3cm.把△ABC绕点A顺时...
在Rt△ABC中,∠C=90°,BC=4cm,AC=3cm.把△ABC绕点A顺时针旋转90°后,得到△AB
1C
1,如图所示,则点B所走过的路径长为( )
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103102446931193624/SYS201311031024469311936004_ST/images0.png)
A.5
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103102446931193624/SYS201311031024469311936004_ST/0.png)
cm
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103102446931193624/SYS201311031024469311936004_ST/1.png)
πcm
C.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103102446931193624/SYS201311031024469311936004_ST/2.png)
πcm
D.5πcm
考点分析:
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如图,等腰梯形ABCD中,AD∥BC,以A为圆心,AD为半径的圆与BC切于点M,与AB交于点E,若AD=2,BC=6,则
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B.
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C.
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D.
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B.4cm
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阅读下面材料:
对于平面图形A,如果存在一个圆,使图形A上的任意一点到圆心的距离都不大于这个圆的半径,则称图形A被这个圆所覆盖.对于平面图形A,如果存在两个或两个以上的圆,使图形A上的任意一点到其中某个圆的圆心的距离都不大于这个圆的半径,则称图形A被这些圆所覆盖.
例如:图中①的三角形被一个圆覆盖,②中的四边形被两个圆所覆盖.
回答下列问题:
(1)边长为1cm的正方形被一个半径为r的圆所覆盖,r的最小值是______
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