Dan Piponi
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 Nov 30 comment Solve complex equation $|z|^5=z^5$ for $z$ $|z|^5$ is $|z^5|$. So first solve $|a|=a$ and then solve $z^5=a$ for all valid $a$. Aug 30 comment Geometric introduction to exterior algebra dl.dropboxusercontent.com/u/828035/Mathematics/forms.pdf Jul 20 awarded Yearling Jun 22 comment An easy example of a non-constructive proof without an obvious “fix”? I guess what you mean is that the obvious classical proofs of this proposition can't be fixed. I think there may well be some entirely different constructive proof that hasn't been found yet. Jun 1 comment Real world applications of category theory @Niriel Transition went very well. You can read about the actual project here: theverge.com/2013/9/1/4680456/… May 14 revised How many degrees of freedom would a rotation matrix in R5 have? added 97 characters in body May 14 comment How many degrees of freedom would a rotation matrix in R5 have? @loupblanc Yes, quite right. I'll add a comment to the answer. May 14 answered How many degrees of freedom would a rotation matrix in R5 have? May 6 answered Book recommendation on infinitesimals Apr 27 comment Why is $x^0 = 1$ except when $x = 0$? If you're in the combinatorics business, zero is natural. If your business involves primes, zero is not. I'm not sure what people do when they have a foot in both camps. Mar 16 comment Domain of log and its derivative Did you mean to write $(0,\infty)$? The derivative clearly can't exist where the function being differentiated doesn't exist. Mar 12 revised Examples where it is easier to prove more than less deleted 7 characters in body Mar 12 answered Examples where it is easier to prove more than less Mar 12 comment How to explain brackets to young students It sounds like this student has a very good understanding of brackets, something I've seen students struggle with. The problem here isn't with brackets, it's with addition. Mar 12 comment Prove f(a)=f(b) if $\int_{-\infty}^{\infty}f(x)dx=1$ Very roughly: if f(a)>f(b) then shifting the region [a,b] left by δ would increase the integral by approximately δ(f(a)-f(b)) which would then allow you to shrink the length of the interval and still achieve the same integral. Mar 3 awarded Popular Question Feb 11 awarded Nice Answer Dec 19 awarded Caucus Dec 15 comment Are the real numbers really uncountable? @CarlMummert I'm not trying to say anything profound. Typically, in mathematics, when you want to pick a particular thing (in ZF, say) to talk about, you use a definition. Dec 15 comment Proving $\int x \, \mathrm{d}y =xy- \int y \, \mathrm{d}x$ $\frac{dy}{dx}$ might look like a straightforward fraction, but it's not. You can't simply cancel $dx$'s without further justification.