am I making some kind of basic algebra mistake?

[Kuciwalker]

A surface wave in deep water originated some unknown distance away. At time 0 we first observed the wave and it had period T1. At time t we observed the wave again and it had period T2. We know omega = 2*pi/T and omega^2 = g/L => L = g*(T/2*pi)^2. cg^2 = g*L => cg = g*T/(2*pi). d = t*cg1*cg2/(cg1-cg2) = twice the book's answer.

T = period, L = wavelength, g = gravity, cg = group velocity, d = distance

edit: I fixed my stupid eqn for d, but I'm still off by a factor of 2 somewhere

[Asher]

Wouldn't be the first time the back of the book is wrong.

[Hauldren Collider]

Wait, where does that equation for d come from?

This math is probably above me...

Also quick and possibly retarded observation: If they're looking for distance at time 0 then (some velocity)*t is not going to get you the answer unless it's moving away from you

[loinburger]

Wouldn't be the first time the back of the book is wrong.

One time I had the 3rd edition of the book and everybody else had the 4th edition (because the 3rd edition cost about 10% as much as the 4th). The only difference was that the problems in the back were in a different order, and in the 4th edition several problems were inexplicably given the wrong answer.

[Kuciwalker]

HC:

The equation for d comes from me being retarded. It's actually d = t*cg1*cg2/(cg1 - cg2). And no, the math is well within your ability.

[giblets]

I tried it and also got cg = gT/(2π)

[Hauldren Collider]

I would try to help more but my calc teacher thinks it prudent to teach us how to do Euler approximations and the trapezoid rule by hand.

**** the trapezoid rule. just **** it.

[Ben Kenobi]

The algebra seems fine.

Did you plug in the correct factors?

[Hauldren Collider]

Lol. Somehow I doubt BK would be able to supply any useful math advice to Kuciwalker.

EDIT: Viewed post, and surprise! I was right.

[giblets]

I'm surprised he didn't say something wrong in order to troll people.

[Ben Kenobi]

Somehow I doubt BK would be able to supply any useful math advice to Kuciwalker.

DL, I've done honours physics and astronomy, similar stuff to what Kuci is doing now. Of course you know everything about everyone here, so please continue to spout off.

useful math advice to Kuciwalker.

His math is correct. I don't see what else I can possibly add to the discussion regarding his calculations. I checked the same figures as you did and I get the same answer.

What would you like me to say?

[Ben Kenobi]

I'm surprised he didn't say something wrong in order to troll people.

Look, DL, I don't troll sincere requests for help. Ever.

[The Emperor Fabulous]

I see the problem here, Kuci: you're using letters. Math is made up of numbers, bro.

[David Floyd]

[Hauldren Collider]

DL, I've done honours physics and astronomy, similar stuff to what Kuci is doing now. Of course you know everything about everyone here, so please continue to spout off.

ROFL

You are not even 1% as smart as Kuciwalker. Especially at math. It's just not possible.

His math is correct. I don't see what else I can possibly add to the discussion regarding his calculations. I checked the same figures as you did and I get the same answer.
What would you like me to say?

I'd like you to shut up because you're an idiot and suck at math.

I know maybe two or three people who are better at math than Kuciwalker and for almost my entire life I've been surrounded by geniuses. And you are definitely not a genius.