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标题: TT GWD 6-30 [打印本页]

作者: alexmingzhu 时间: 2006-10-7 20:00 标题: TT GWD 6-30

The circle shown has center R. If arc UST has length 48π, what is the radius of the circle?

A. 18

B. 24

C. 32

D. 48

E. 64

I am sorry that I cannot draw the circle here. But I have searched the related discussion and could not figure it out. Can sb tell me why the answer is C?
thanks

作者: assurance 时间: 2006-10-8 06:35

arc UST这段圆弧的周长占整个原周长的3/4(因为剩下的圆弧UT是1/4个圆周)，所以有：

2πr×3/4=48π

解出r=32

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