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Sketch the graph of the function \(f(x) = \ln(\cos(x)),\)
and consider the segment of this graph
between the points \((0,f(0))\) and \((\pi/3,f(\pi/3))\).
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Calculate the arclength of this segment.
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Consider the surface that results
from revolving this segment about the \(y\)-axis.
Sketch this surface.
Write down an integral that expresses
the area of this surface.
Play with this integral until you suspect,
as I suspect, that evaluating it by hand
is very difficult.
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Consider the surface that results
from revolving this segment about the \(x\)-axis.
Sketch this surface.
Write down an integral that expresses
the area of this surface.
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Based on your sketches,
which of these two surface areas will be larger?
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Demonstrate how to evaluate the integral
expressing the latter surface area.