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

jinjing 2010-05-26 15:14:20 ( reads)

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.

跟帖(2)

AnaZhang

2010-05-26 18:36:36

Agree with your answer

guest007

2010-06-02 09:14:07

Thanks, I did not know that word before