Mathematics Stack Exchange
Mathematics Stack Exchange

Questions tagged [notation]

Questions on the meaning, history, and usage of mathematical symbols and notation. Please remember to mention where (book, paper, webpage, etc.) you encountered any mathematical notation you are asking about.

Before asking a question on the site, please check if you can find your answer in Earliest Uses of Various Mathematical Symbols or the book A History of Mathematical Notations.

Alternatively, a textbook or paper usually takes the time to explain the notation they're using; please remember to mention where you've seen the notation you are asking about.

12848 questions
2
votes
1 answer

Notation "set over integer"

I'm reading a paper about graph theory and can't guess what could be meant with the Notation "$I\in\binom{V(G)\times V(H)}{\ell}$", where $\ell\in\mathbb{N}$ and $V(G),V(H)$ sets (of vertices of the graphs $G,H$). Later the notation…
algebrah
  • 133
2
votes
1 answer

Question about notation to depict multiplication $\cdot$ or $\star$ or nothing at all?

I see different documents using $\cdot$ or $\star$ to depict multiplication. For e.g. some use $4.5.6 = 120$ while others may be use $4\star 5\star 6 = 120$. And in case it involves brackets, I also see stuff like $e(x) = f(x)g(x)h(x)$ or $e(x) =…
user93353
  • 466
  • 2
  • 18
2
votes
2 answers

How to indicate keeping the sign when squaring a number.

I have a vector $x$, which I wish to transform according the the following computer code xstar = sign(x) * x^2 with $x^*$ preserving the positiveness or negativeness of $x$. How would I write this in proper mathematics? Obviously $x^2$ is…
gregmacfarlane
  • 1,729
2
votes
1 answer

Symbol for obliqueness.

Is there a universally recognised symbol for "is oblique to"? After all, there is $\parallel$ for "is parallel to" and $\perp$ for "is perpendicular/orthogonal to". Using $\require{cancel}\cancel\parallel$ is ugly and cumbersome, in addition to…
GPWR
  • 203
  • 1
  • 8
2
votes
1 answer

Can this anomaly of the unary base system be generalized?

I observed a strange anomaly in the sequence of bases of a number system. For every $n$-base, $n \geq 2$, it holds that its number symbols are written with numerals which are all less than $n$. For example, a binary ($2$-ary) base has number symbols…
God bless
  • 2,049
2
votes
0 answers

In which direction does $\overset{def}{=}$ "act"?

One symbol used for defining objects is "$\overset{def}{=}$". Let's say we introduce a new symbol $B$ which should be defined as $A$. Is $\overset{def}{=}$ then used as $$ A\overset{def}{=}B $$ or $$ B\overset{def}{=}A $$ or is this just a…
HerpDerpington
  • 341
2
votes
1 answer

How do I write "each $a$ belongs to a certain $b$

I have two types of elements: $a$ and $b$. Each $a_i \in A$ belongs to only one specific $b_j \in B$. e.g. $a_1, a_2, a_3 \in b_1, \\ a_4, a_5 \in b_2$ I could use some help with writing this in a nice mathematical expression. So far I came up…
Chris_abc
  • 123
2
votes
4 answers

Composing function

The function is $f: \Bbb{R}\rightarrow\Bbb{R}$ defined as $f(x)= 2/ (x -3).$ I need to find $(f o f)(1).$ I would like to ask which of the following answers are the right one for writing this function. $( f o f) ( 1 ) = ( f ( f ( 1 ) ) )= ( f ( 2/ 1…
Petar Atanasov
  • 21
2
votes
0 answers

Should I use $\{\}$ or $()$ to denote an element of a Cartesian product?

Let $X=\{X_1,\dots,X_n\}$ be a finite collection of finite sets $X_i$. Let \begin{gather} \prod_{i\in N}X_i \end{gather} be its Cartesian product. I have seen an authoritative reference in my field denote an element of this Cartesian product…
EoDmnFOr3q
  • 1,050
2
votes
0 answers

Is there formal guidance on when equations should be aligned at the equals sign?

There are plenty of resources out there explaining how to align multiple lines of equations at the equals sign. But I can’t find anything that says when this should be done. Does any style guide, ISO standard, or similar publication address…
Tim Pederick
  • 738
2
votes
2 answers

Set Notation and usage

I am working on a write-up and want to say that a variable is a positive integer (including zero). Would this be said as "variable is in the set of all nonnegative integers"? Maybe there is a different notation I should be using? In the event that I…
Breadleaf
  • 121
2
votes
0 answers

Is f((x,y)) equivalent to f(x,y)

I was writing an article and I stumbled across a situation where I was doubting how to be rigorous in my writing. I'm going to give an example to illustrate the problem. Let $X = \{(x, y, z), x, y, z \in \mathbb{R}\}$. Now we want to construct a…
Sakoboy
  • 21
2
votes
0 answers

Notation Problem

I'm reading a paper that uses the notation $[f]^+_-$ for a function f. Anyone know that this means? More explicitly it appears as $$ \frac{1}{{[U_0]}^+_-} \int^{\infty}_{-\infty}U_{0z}^2 \, \mathrm{d}z$$
user17904
  • 291
2
votes
2 answers

Acceptable to write $\sup\,\{f(x) \mid x \in \mathbb R\}$ as $\sup\,\{f(x)\}_{x \in \mathbb R}$?

Is it acceptable to write $\sup\,\{f(x) \mid x \in \mathbb R\}$ (where $f\colon \mathbb R \to \mathbb R$) as $\sup\,\{f(x)\}_{x \in \mathbb R}$? I have seen it written as $\sup\limits_{x \in \mathbb R}f(x)$, but never as $\sup\,\{f(x)\}_{x \in…
user83343
  • 45
2
votes
1 answer

Good notation for repeated equality

If I wanted to write the repeated union of sets $A_1 \cup ... \cup A_n$ I could write this succinctly using big union notation as $$ \bigcup_{i=1}^n A_i $$ How can I best express that all $A_i = ... = A_n$ are equal to each other using 'big…
Jedf
  • 123
1 2 3
…
99 100