calaulos~~~也很急!!!!!!
2007-01-24 4:32 pm
At a ertain instant, the area of a circular plate is increasing at the same rate as its radius increasing. What is the radius at that instant?
回答 (1)
2007-01-24 5:19 pm
✔ 最佳答案
A=πr^2dA/dt
=(2πr)(dr/dt)
since the area of a circular plate is increasing at the same rate as its radius increasing
So let dA/dt=dr/dt=x
dA/dt=(2πr)(dr/dt)
x=(2πr)x
1=2πr
r=1/2π
the radius at that instant is 1/2π
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https://hk.answers.yahoo.com/question/index?qid=20070124000051KK00526