User:GFauxPas/Sandbox

Welcome to my sandbox, you are free to play here as long as you don't track sand onto the main wiki. --GFauxPas 09:28, 7 November 2011 (CST)


 * $u \ v \ \mathsf{u} \ \mathsf{v} \ \nu \ \upsilon$

Anyone else have a hard time distinguishing between $u$ and $v$? I would like it to look more like this, does it confuse anyone else? It seems PW doesn't have the upgreek package. --GFauxPas 07:49, 27 January 2012 (EST)


 * Nope. Multiple years of extensive TeX writing and reading have trained my eye. I agree that referenced $v$ looks more distinguished, but imagine it is hard to implement. --Lord_Farin 08:08, 27 January 2012 (EST)

Derivative of a Series?
I'm learning convergence and divergence of sequences and series in my Calc Class, and Larson is implicitly using a theorem here, and it seems significant enough to warrant a page on PW if it's not already up, can someone explain what he did here?

The book is analyzing:


 * $\displaystyle \sum_{n=1}^{\infty} \ (-1)^n \frac {\sqrt{n}}{n + 1}$

He wants to use the Alternating Series Test, so to prove that $a_{n+1} \le a_n$, he creates a differentiable real function:


 * $f(x)= \displaystyle \frac {\sqrt{x}}{x + 1}$

and takes the derivative of that. That proves that $f$ is a decreasing function (for $x > 1$) but how does it prove that:


 * $\left \langle{ \displaystyle \frac {\sqrt{n}}{n + 1}}\right \rangle$

is decreasing? --GFauxPas 20:45, 4 February 2012 (EST)

Infinite Limit
I'm looking at the proof for Infinite Limit Theorem and I'm stuck, I think Larson is assuming that:


 * $\left({a > b \land c > d \land a, b, c, d, > 0 }\right) \implies \dfrac a c > \dfrac b d$

Is there such a theorem? --GFauxPas 00:06, 5 February 2012 (EST)


 * No, because it does not hold: Real Ordering Incompatible with Division. --prime mover 04:22, 5 February 2012 (EST)