Intereting Posts

Direct product and normal subgroup
Extending the logical-or function to a low degree polynomial over a finite field
Finite abelian $p$-group with only one subgroup size $p$ is cyclic
How to approach solving $\int_0^{\pi/2} \ln(a^2 \cos^2 x +b^2 \sin^2 x ) dx$
Minimal embedding of a group into the group $S_n$
Euler's remarkable prime-producing polynomial and quadratic UFDs
Why does 0! = 1?
$\int_{-\pi/2}^{\pi/2} \frac{\sin^{2012}{x}}{\left(1+ \alpha^x\right)\left(\sin^{2012} {x}+\cos^{2012}{x}\right)}\;{dx} $
An apex of a cyclically ordered group
Is $e^{|x|}$ differentiable?
IMO 2016 P3, number theory with the area of a polygon
Sylow 2-subgroups of the group $\mathrm{PSL}(2,q)$
If $H$ is a cyclic subgroup of $G$ and $H$ is normal in $G$, then every subgoup of $H$ is normal in $G$.
What are the rules for equals signs with big-O and little-o?
Intersection between two planes and a line?

Frequently, when referring to the edges of an undirected graph $G=(V,E)$, I want to write that $E \subset V \times V$, which isn’t correct since the Cartesian product is ordered and the edges are not.

This motivates my question: is there a common notation for a product of sets $A$ and $B$ defined by $\{ \{a,b\} ~|~ a \in A ,~ b \in B \}$?

- Image of the set of natural numbers under any function is denumerable.
- Recursive Mapping
- Proper notation for distinct sets
- if $f: (0,\infty) \to (0,\infty)$ is a strictly decreasing then $f \circ f$ is decreasing?
- References for relations between and classification of different set systems?
- Factorial of Infinite Cardinal

- Is there an infinite countable $\sigma$-algebra on an uncountable set
- A intersection (A union B)
- Prove that if $Z\subseteq Y$, then $(g\circ f)^{-1}(Z)=f^{-1}(g^{-1}(Z)).$
- Double Complement of a set proof
- Is the null set a subset of every set?
- Prove that $f$ is one-to-one iff $f \circ h = f \circ k$ implies $h = k$.
- When does it make sense to define a generator of a set system?
- Why are x and y such common variables in today's equations? How did their use originate?
- Proof of complement of intersection defined using an arbitrary set.
- Elementary set theory homework proofs

I use $E \subseteq \binom{V}{2}$. Although, I have seen it used elsewhere, it’s probably not a standard notation.

We used $\bar{\times}$ (but without the gap between the bar and the times symbol) in the algebraic graph theory lectures I’ve attended some years ago. I liked it, however I don’t know how common it is.

- Is a probability of 0 or 1 given information up to time t unchanged by information thereafter?
- Explain these ring isomorphisms
- Finitely generated idempotent ideals are principal: proof without using Nakayama's lemma
- Using permutation or otherwise, prove that $\frac{(n^2)!}{(n!)^n}$ is an integer,where $n$ is a positive integer.
- Sum of two squares $n = a^2 + b^2$
- If $a+b+c=0$ and $\{a,b,c\}\subset$ so $\sum\limits_{cyc}\sqrt{1+a+\frac{7}{9}b^2}\geq3$
- What is the fallacy in this proof?
- Contour Integral $ \int_{0}^1 \frac{\ln{x}}{\sqrt{1-x^2}} \mathrm dx$
- Is Godel's modified liar an illogical statement?
- No group of order $400$ is simple – clarification
- Proving that the length of the sum and intersection of two finite length modules is finite.
- Euler's Totient function $\forall n\ge3$, if $(\frac{\varphi(n)}{2}+1)\ \mid\ n\ $ then $\frac{\varphi(n)}{2}+1$ is prime
- how do you do this integral from fourier transform.
- Smooth functions for which $f(x)$ is rational if and only if $x$ is rational
- Rule for multiplying rational numbers