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Jun
13
comment Prove that the product of a rational and irrational number is irrational
It's surely not quite correct. For example, you missed factors of $1/z$ and $1/b$ in evaluating or "simplifying" $xy/z=a/b$. Otherwise the logic is OK.
Jun
12
awarded  Nice Answer
Jun
12
answered How do I combine multiple sets of ratios in order to meet an overall “target” ratio? (word problem supplied to illustrate)
Jun
12
answered K3 surface criteria
Jun
12
comment Is there an analogue to the “Delta” symbol for ratios?
Dear Theo, what I mean by "discontinuous" is that there is no continuous $f(x)$ such that $f(0)$ is positive and $f(1)$ is negative so that $f(k)/f(0)$ which is $\Delta^\times x$ at some moment would be well-defined for all $k$ between $0$ and $1$. That's a warning sign - if one uses $\Delta^\times$ for things that change sign, it could be an unnatural thing that can go awry at moment... I know that $\Delta$ is the Greek counterpart of $D$ but I think it's a good idea to distinguish them. Did your $D$ mean $\Delta$?
Jun
11
comment Is there an analogue to the “Delta” symbol for ratios?
Dear Theo, $\log(-1)=\pi i$ and $\exp(\pi i)=-1$: is there any problem with that? Something's changing multiplicatively but changing sign would be a discontinuous process in the real numbers, anyway, so it only makes good sense in the complex realm. Concerning the notation, not sure whether I understand which $D$ you mean.
Jun
11
revised Is there an analogue to the “Delta” symbol for ratios?
added 176 characters in body
Jun
11
comment Intersection of two vectors using perpedicular dot product
This is really badly readable. Would it be difficult to translate the obscure object-oriented code into normal mathematical language?
Jun
11
answered Is there an analogue to the “Delta” symbol for ratios?
Jun
11
comment Combinatorial proof that binomial coefficients are given by alternating sums of squares?
OK, sorry, I probably don't know what a combinatorial proof is. If that's pictures, I was taught that the most beautiful picture is an equation. ;-)
Jun
11
answered Combinatorial proof that binomial coefficients are given by alternating sums of squares?
Jun
11
revised Question about Holomorphic functions
added 159 characters in body; added 780 characters in body
Jun
11
comment Question about Holomorphic functions
Pleasure. Maths is trivial - once it's proved. ;-)
Jun
11
answered Question about Holomorphic functions
Jun
10
comment p chance of winning tennis point -> what f(p) chance of winning game?
Thanks for the great edits, @Chris! You're a co-author. ;-) That's exactly what I saw in Mathematica.
Jun
10
revised p chance of winning tennis point -> what f(p) chance of winning game?
added 352 characters in body
Jun
10
answered p chance of winning tennis point -> what f(p) chance of winning game?
Jun
10
answered Integral of $\sqrt{1+\tan^2x}$
Jun
10
answered Applications of systems of linear equations
Jun
10
answered evaluating a complex integral where the integrand is analytic within the contour but not necessarily analytic on the contour