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January 11th, 2009, 04:04 PM   #1
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Minimizing the length of a fold with differentiation

Hello. I'm studying for my Calculus exam, and I'm stumped on one of the review questions in my textbook.

A legal-sized sheet of paper (8.5 in by 14 in) is folded so that corner P touches the opposite 14 in edge at R. (PQ=?C^2-x^2)

Here's the image given (sorry for th size):


a) Show that C^2=(2x^3)/(2x-8.5)
b) What is the domain of C?
c) Determine the x-value that minimizes C.
d) Determine the minimum length C.

I had a friend help with me with this problem, but the work turned out be Calculus 3 work. Obviously, it didn't help me much.

The only idea I have is you use the Pythagorean Theorem, starting with the top left right triangle(?)
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January 11th, 2009, 04:24 PM   #2
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Re: Minimizing the length of a fold with differentiation

This might help you: http://www.math.ucdavis.edu/~kouba/C...l#PROBLEM%2021
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January 12th, 2009, 01:01 PM   #3
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Re: Minimizing the length of a fold with differentiation

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Originally Posted by greg1313
Perfect! Now, I understand. Thank you!
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