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July 22, 2014

July 22, 2014

Posted by **Taeyeon** on Sunday, February 26, 2012 at 4:13pm.

A. 1/4pi B.1/4 C.1/pi D. 1 E.pi

- calculus -
**MathMate**, Sunday, February 26, 2012 at 8:11pmArea = πr²

dA/dr=2πr

dA/dt=dA/dr*dr/dt=2πrdr/dt

So when dA/dt=2dr/dt

2πrdr/dt=2dr/dt

r=1/π

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