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Math Forum » Discussions » sci.math.* » sci.math.independent

Topic: Area and volume of solid of revolution
Replies: 14   Last Post: Nov 28, 2005 11:13 PM

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RCA

Posts: 11
Registered: 11/26/05
Re: Area and volume of solid of revolution
Posted: Nov 27, 2005 1:40 PM
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Kyle wrote:

"When finding solids of revolution we first evaluate an
integral that calculuates the *area under a curve* and
then rotate that quantity.


When finding surfaces of revolution we evaluate an
integral that calculates the *length of a curve* and
then rotate that quantity. "

Agreed, Kyle. My question is - why does the area under the curve
calculation ignore the "arc length" aspect. The arc length is used as
the basis for the surface area of revolution while the arc length is
approximated to the x component while calculating the volume (or the
area under the curve). I dont understand how that is justified.

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