near (400/Pi)*li, You are right.

来源: jinjing 于 2010-05-26 15:14:20 [] [旧帖] [给我悄悄话] 阅读数 : (126 bytes)
回答: 轮子上一点移动多少距离？ 由 guest007 于 2010-05-26 08:47:03

x=r(1-sint)
y=r(1-cost)
ds=2^.5r(1-cost)^.5dt,s=Intg(2^.5r(1-cost)^.5dt)from 0 to 2Pi= 8r, so (100/2Pi*r)*8r=(400/Pi)li.

所有跟帖： 

• Agree with your answer -AnaZhang- ♀ 给 AnaZhang 发送悄悄话 AnaZhang 的博客首页 (148 bytes) () 05/26/2010 postreply 18:36:36

• Thanks, I did not know that word before -guest007- ♀ 给 guest007 发送悄悄话 (54 bytes) () 06/02/2010 postreply 09:14:07

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