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
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when a negative sign follows a division sign, what is on the right hand side of the division sign?

This is a bit of a dumb question (and not a very useful one either), but nonetheless: I've been taught that grammatically, the negative sign is actually just negative one being multiplied with the number on its right. Thats why $-x^2$ is practically…
Evan
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What is the "II" set operation called?

I'm reading "General Topology" by Muller and he uses $$A \amalg B = \{(1, a) | a ∈ A\} ∪ \{(2, b) | b ∈ B\}.$$ Does this operation have a name or a different symbol? I've never seen it before.
djeastm
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Looking for a mathematical notation for array element assignments, without using summation or product

I am looking for the appropriate mathematical notation that will represent this code. for(X = 0; X < ACA_Bin.size; X++) { ACA_CORRECTION[X] = ACA_Bin[X] + ACA_OFFSET } This is not a summation or product that would require a Sigma Notation So is…
MoMan
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What does $\langle2\rangle$ mean?

What does $\langle2\rangle$ mean? I encountered it in the context of $\mathbb{Q}_2$ and it seemed most likely to mean something like $\{2^z:z\in\mathbb{Z}\}$ from what I could deduce but I've been unable to find a reference to it.
it's a hire car baby
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Alternative to subscript notation?

I have a variable $K$, that is the sum of its components $K_a$, $K_b$, $K_c$. Now I want to describe a set of $K$'s, but I can't use $K_i$ because I already used the subscript notation to differentiate between the components of $K$. I don't want to…
Yousef Amar
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Are ".x" and "x." correct number notations?

I know that sometimes the notation .x is used as a short form of 0.x, but I've never heard about x. being a correct number (for instance, 3.). I want to know if it's technically correct to use a short-hand notation with leading/ending dot instead of…
Ivan Yurchenko
  • 131
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How to express a vector which is retrieved from a matrix

How to express a vector which is retrieved from a matrix. In other words, suppose I have a matrix $\mathbf{B},$ y is a the first column vector of the matrix. I am looking for the notation which is involved the matrix.
Ray
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Notation for much smaller subset

Similar to $x \ll y$ or $x \lll y$, I'm wondering if there is a corresponding symbol for subsets. For example: $$x \subset \subset y$$ Something to represent $x$ is subset of $y$, but much smaller in size than $y$. I realize one could simply say $x…
ryan
  • 81
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What does this triangle pointing right symbol mean?

In the third step below, what does the little triangle pointing right mean? Sum of roots: \begin{align}\alpha+\beta&=-\frac 53 \cdots \tag{1}\\[6pt] \alpha-\beta&=\frac 73\cdots \tag{2}\end{align} $(1)+(2)$: \begin{align}2\alpha&=\frac…
Kex
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What is the type of letter $\mathbb {A,B,C,D,...}$ called

$\mathbb {N,P,Q,R,Z}$ all represent commonly used sets of numbers, but I can't find any good references on what they're called. I've tried double bar, double stroke, and googling what the ____ number symbol was called; inserting for integers,…
Jacob Claassen
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Can't understand parts of a question

I am working on a math exercice : Let $E$ be a non-empty set and $f : E \to \mathcal{P}(E)$, a function. a) Let $A = \{x \in E \mid x \notin f(x)\}$. Let $x \in E$. Show that $x \in f(x) \cup A$ and that $x \notin f(x) \cap A$. Deduce from that that…
Pop Flamingo
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What does the operator $\mathop{\large\mathrm K}_{i=1}^\infty$ stand for?

There are many different operators, for example sums $$\sum_{i=1}^\infty$$ or products $$\prod_{i=1}^\infty$$ But what does this operator stand for? What does it mean? $$\mathop{\LARGE\mathrm K}_{i=1}^\infty$$ I am sorry for this might being a dumb…
G. Ünther
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interval has one element {how to write it} symbol

If we have interval has one element for example $[a,a]$ Is it wrong to write it in the form $ [a,a] $? We write it as $\{a\}$ Thank you :)
AbdulQader
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How can $4 \cdot 7=28=1 \bmod 9$?

I was reading this article about RSA that « reader who only has a beginner level of mathematical knowledge should be able to understand » but I must be really quite dumb because I couldn't figure out that part : Lets work in the set $\mathbb{Z}_9$,…
Frank Malenfant
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Sentence ending with a number and an exclamation point

Suppose you want to emphasize some idea and your sentence ends with a number. You want to be clear to the reader that you do not mean factorial. For instance, you wish to emphasize When using method $ABC$, your approximation is off by a factor of…
D Poole
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