- #1

doug1122

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## Homework Statement

If you take an 8.5in by 11in piece of paper and fold one corner over so it just touches the opposite edge as seen in figure (http://wearpete.com/myprob.jpg ). Find the value of x that makes the area of the right triangle A a maximum?

## Homework Equations

A = 1/2(xy)

x

^{2}+y

^{2}=(8.5-y)

^{2}

## The Attempt at a Solution

x

^{2}+y

^{2}=(8.5-y)

^{2}

x = sqrt((8.5-y)

^{2}-y

^{2})

A = 1/2(y)(sqrt((8.5-y)

^{2}-y

^{2}))

da/dx = ((y

^{2}-4.25y)/sqrt((8.5-y)

^{2}-y

^{2}))+1/2(sqrt(-17y-72.25))

I know that at da/dx=0 the triangle is maximized but da/dx is undefined at y=0 (y graphically). I am pretty sure my derivative is right but maybe I missed something there. Thanks for taking a look.

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