Math Is Fun Forum

Kryptonis

Member

Registered: 2011-03-03

Posts: 11

Length of a curve

x = t / (3+t) y = ln(3 + t) 0 ≤ t ≤ 4

Here's the problem, my real question lies in the answer...

-sqrt(u^2 + 9)/(u) + ln(u + sqrt(u^2 + 9)) with the lower @ 3 and the upper @ 7
where u = t + 3 and du = dt

When I integrate, I'm at a loss as to how i should be coming up with -sqrt(u^2 + 9)/(u) + ln(u + sqrt(u^2 + 9)).
As I keep coming up with -sqrt(u^2 + 9)/(u) + ln(sqrt(u^2 + 9).

Last edited by Kryptonis (2011-03-11 22:07:55)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Length of a curve

Hi;

Did you start off like this?

Then did you use this formula?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

soroban

Member

Registered: 2007-03-09

Posts: 452

Re: Length of a curve

. . . . . . . . . . .

. . I'll let you verify my trig identities.

.