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As in figure 2.In the circular ring of which center is point O.if AO⊥BO，and the area of the shadowy part is 25cm2，then t

分类: 作业答案 • 2022-01-09 18:02:33

问题描述：

As in figure 2.In the circular ring of which center is point O.if AO⊥BO，and the area of the shadowy part is 25cm²，then the area of the circuiar ring equals to（　　）（π≈3.14）
A. 147cm²
B. 157cm²
C. 167cm²
D. 177cm²

答

设大圆的半径为R，小圆的半径为r，
∵AO⊥BO，
∴阴影的面积为两个直角三角形的面积之差，
∴R²-r²=50，
∵圆环的面积为两个圆的面积之差，
∴圆环的面积=π（R²-r²）=50π=157cm²．
故选B．

As in figure 2.In the circular ring of which center is point O.if AO⊥BO，and the area of the shadowy part is 25cm2，then t

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