AlexR
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 1d comment Topological space $\nRightarrow$ Metric space $\nRightarrow$ Normed space $\nRightarrow$ Inner product space (Examples) The discrete metric is the standard example to break norms. For non-inner product spaces there are plenty of options in infinite dimensional function spaces (such as $L^\infty$) 1d comment Sum of $\sum\limits_{x=-\infty}^{\infty}x^{\operatorname{sign}(x)}$ I don't count any fourier analyst to "most people" then... Technically, in analogy to improper integrals, $$\sum_{n=-\infty}^\infty a_n := \lim_{k\to\infty} \sum_{n=l_k}^{m_k} a_n$$ For any sequences such that $l_k \to -\infty$ and $m_k \to \infty$. Well-definedness of said thing can be worked out if $$\lim_{N\to\infty} \sum_{n=-N}^N |a_n| < \infty$$ This allows simplification in case of convergence to $$\sum_{n=-\infty}^\infty a_n = \lim_{N\to\infty} \sum_{n=-N}^N a_n$$ 1d comment What are the numbers in an inequality called? @noumenal No, I know the difference between id est and exemplum gratias :P I was hinting at $1<4$ not being a set (but instead an inequality). A set of inequalities would be $\{1<4, 42 < \pi^2\}$ (not necessarily true) or $\{1<4\}$. 1d comment What are the numbers in an inequality called? @noumenal $1<4$ is not a set of inequalities^^ Maybe you should define it as a function of two expressions instead? This would then seem to be $$f(x,y) = \frac xy \qquad \text{where } x < y$$ 1d comment What are the numbers in an inequality called? @noumenal People will understand you better if you use LHS and RHS respectively, given that you don't have a chain of inequalities. In this case you could say "the LHS of the $n$-th inequality"... 1d comment Inverse Permutations from $S_7$ The inverse of $(12357)^{-1}$ is obviously $(12357)$... Maybe you want its inverse instead? 2d comment Find the greens function of the following non homogeneous problem: Apart from the formatting issues, the problem statement is incomplete without some information on the RHS $f(x)$ 2d comment Usefulness of prime numbers as Threading Timeouts in programming Note I said that the UNIT is arbitrary. And yes, chosing coprime tineouts will maximize their gcd given that they are accurately obeyed. Jul1 comment Usefulness of prime numbers as Threading Timeouts in programming It is disputible. Note that the time unit of milliseconds is completely arbitrary. Your "prime timeouts" are all multiples of 1000 when measured in CPU time (= nanoseconds). Also note that to prevent such synchronisation effects, it's best to pick a random timeout within a fixed range. Jul1 revised Find the greens function of the following non homogeneous problem: edited tags Jul1 comment Find the greens function of the following non homogeneous problem: Please edit your post to make it more readable. For some basic information about writing math at this site see e.g. here, here, here and here. Jul1 comment Usefulness of prime numbers as Threading Timeouts in programming Nope. How are you even going to make sure your millisecond-waits are accurate to the millisecond? (Think of Heavy loads). Also, how do you think a "harmonic (oscillation)" in a computer program could possibly produce a glitch / bug / whatever? Jul1 comment Finding circumference of a circle with a hole in it How should the red thing be defined? The two circles only intersect in (at most) two points, not an arc. Jul1 revised Finding circumference of a circle with a hole in it deleted 38 characters in body Jul1 comment What is the Fourier transform of Riemann Zeta function? A discrete fourier transform of a function defined on a continuous set... Do you even know what you're talking about? Jun30 comment How do i find $\tan(\theta)$ such that : $\frac{16}{\sin^6(\theta)} + \frac{81}{\cos^6(\theta)}=625$?? diophantine-equations are a completely unrelated topic. Please read the tag description before applying a tag. Jun30 revised How do i find $\tan(\theta)$ such that : $\frac{16}{\sin^6(\theta)} + \frac{81}{\cos^6(\theta)}=625$?? edited tags Jun30 comment Finding the best direction for a bird escape from a radiation (function of 3 parametres) @user183297 The symmetry implies a gradient of $(0,0,0)$ in the point of symmetry, but not the other way. Imagine a bump with ellipses as equipotential lines. The center of the ellipse will still have a gradient of $(0,0,0)$, but clearly an ellipse isn't rotationally symmetric. Jun30 comment Touch times to authenticate user Please flag it for the mods. They will migrate your question to stats.SE. Jun30 comment Any shortcut method to compare the roots of two quadratic equations? In wich way do you want to "compare" them? Please clarify your question so that it becomes answerable in this format.