2,348 reputation
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bio website asmeurersympy.wordpress.org
location Austin, TX
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visits member for 3 years, 8 months
seen Apr 12 at 1:29

I am a software developer at Continuum Analytics. I am also the lead developer for the SymPy project.

I will gladly license my code snippets under something more permissive than StackExchange's CC-BY-SA if you want. Consider my work here to be public domain.


Dec
16
comment Linear-Regression Result Accuracy as a Function of Slope, Other Factors
I wonder if this would be better asked on Computational Science SE.
Dec
16
reviewed Reviewed Riemann Integrable $f$ and Real Analysis Proofs
Dec
16
comment Is the skill to learn new math by reading textbook alone (no lectures) required when one becomes a PhD student?
Should this be on Academia SE?
Dec
16
comment Is the skill to learn new math by reading textbook alone (no lectures) required when one becomes a PhD student?
When you get to the point where you are learning things from research papers in journals, you don't have any other choice.
Dec
16
answered Why don't we define “imaginary” numbers for every “impossibility”?
Dec
10
comment Why must we distinguish between rational and irrational numbers?
$\mathbb{Q}$ sits inside of every field of characteristic zero (isomorphically). That makes it very important from an algebraic perspective.
Dec
4
comment $x$, $y$, $x+y$ and $x-y$ are prime numbers. What is their sum?
Sure. It just sounds the way you've written it like you are saying it's $x - 2$ because that is the smallest. But I see now that you were just pointing out that that was the smallest, probably implicitly alluding to my argument above.
Dec
4
comment $x$, $y$, $x+y$ and $x-y$ are prime numbers. What is their sum?
The answers below also prove that there is a unique solution, which your guess gives you no reason to believe.
Dec
4
comment $x$, $y$, $x+y$ and $x-y$ are prime numbers. What is their sum?
As with the other answer, there is no reason a prori to conclude that the smallest of the numbers must be 3. You either have to note that $x - 2$ would be less than 2 if $x$ or $x + 2$ were 3, or else just test all three possibilities ($x - 2=3$, $x=3$, and $x+2=3$) and note that only one of them gives three primes for $x - 2$, $x$, and $x + 2$.
Dec
4
comment $x$, $y$, $x+y$ and $x-y$ are prime numbers. What is their sum?
The only reason it's the smallest of the three is that otherwise $x - 2$ is less than 2, the smallest prime. If the set were $\{x - 1, x, x + 4\}$ (for example), we could also conclude that one of the numbers must be 3, but in this case, the smallest element, $x - 1$, cannot be 3 (because then $x$ would be 4, which is not prime).
Dec
4
awarded  Good Answer
Dec
3
comment Lebesgue Integrable Function
Are you sure he didn't ask $\lim_{k\rightarrow \infty}\int f(x)e^{-x^2/k}\,dx$? In that case, you need to justify switching the integral and the limit.
Dec
2
answered Why $\displaystyle f(z)=\frac{az+b}{cz+d}$, $a,b,c,d \in \mathbb C$, is a linear transformation?
Nov
30
awarded  Mortarboard
Nov
30
comment How to explain that division by $0$ yields infinity to a 2nd grader
I assumed from the question that they at least knew what division was (and thus they probably know what multiplication is as well).
Nov
30
awarded  Nice Answer
Nov
30
comment How to explain that division by $0$ yields infinity to a 2nd grader
I seem to remember being able to understand such things, but then again, I was much better at math than my peers in 2nd grade.
Nov
30
comment Notation for repeated application of function
I wonder if my professor invented this notation (he also wrote the textbook for the class, so it's hard to say). It makes sense, as $\circ$ is the notation for function composition. I personally prefer just $f^n(x)$, though, when the context is clear. Writing all those $\circ$s gets a little annoying after a while :)
Nov
30
comment How to explain that division by $0$ yields infinity to a 2nd grader
@JesperE but for what it's worth, people do work with $1/0=\infty$ in complex analysis all the time (i.e., they work in the Riemann sphere). But you have to be very careful to avoid those indeterminate forms. It's important to do it in the complex case, because you have to identify all infinities as one (e.g., $1/0$ can just as well be $\infty$ as $-\infty$).
Nov
30
comment How to explain that division by $0$ yields infinity to a 2nd grader
@JesperE yes, it does lead to problems. The problem with $\infty$ is that things like $0\infty$, $\infty/\infty$, $\infty - \infty$, and $0/0$ all can't be consistently defined. For example, if you want $\infty - \infty=0$ and $\infty + 1 = \infty$, then you get $\infty + 1 - \infty = (\infty + 1) - \infty= \infty - \infty= 0$ or $\infty + 1 - \infty = (\infty - \infty) + 1 = 1$. So you lose even the most basic rules, like associativity.