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Find the area of the surface obtained by rotating the curve

http://ada.math.uga.edu/webwork2_files/tmp/equations/18/d733a6e52ad8ca260230969bdc3f401.png [Broken]

from x=0 to x=9 about the x-axis.

I'm supposed to parametrize the curve, using rcos(theta) as x and rsin(theta) as y, at least I think I am.

That would give f(x,y) = 3rcos^3(theta),rsin(theta)

Then find the partial derivatives with respect to r and theta and find their cross product. Then find the magnitude of the cross product and integrate with limits int[0-2pi] int[0-9].

Is this right? I can't find any information on the internet to do it this way and the book isn't much help either.

Thanks.

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# Homework Help: Surface area of a rotated curve

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