What is the Rate of change of area of circle in respect to radius when radius is 3in(adsbygoogle = window.adsbygoogle || []).push({});

I know that that dA/dr is equal to the circumference of the circle

But where does that come from?

Also the formula for the circumference of the circle is 2(pi)r

But the answer is 6 (pi)in^2/in.

I understand the 6 but where are the units coming from if the circumference of the circle will only give you units for r ?

Hope someone can shed some light on this for me! Thanks

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# Rate of change of area of circle in respect to radius

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