Posted by Arc Length on Sunday, August 24, 2008 at 9:11pm.
Find the length of the arc formed by
y = (1/8)(4x^22ln(x)) from x=4 to x=8.
I found the derivative of the function and got y'= x(1/4x)
Where I'm lost now is after plugging it into the arc length equation: integral of sqrt(1+(x(1/4x))^2). Squaring the derivative yields me sqrt(1+x^2+1/16x1/2). Help please.

calculus  Damon, Sunday, August 24, 2008 at 9:47pm
I got sqrt [ 1 + x^2 (1/2) + 1/(16x^2) ]
which is
sqrt [ x^2 + (1/2) +1/(16x^2) ]
BUT
x^2 + (1/2) + 1/(16x^2) = [x+ 1/(4x)]^2
ok ?

calculus  Arc Length, Sunday, August 24, 2008 at 10:12pm
Oh yes, sorry, I merely had a typo. I had the same result as you. What I'm confused about is what to do from that point on.

calculus  Damon, Monday, August 25, 2008 at 3:50am
well, the sqrt of that is just
x + (1/4)(1/x)
integral of that is
(1/2) x^2 + (1/4) ln x
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