Mathematics Stack Exchange
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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.

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Notation regarding Balls

What is meant by the notation : $y \in \partial B_\epsilon (x_o)$ Where B is a Ball centred at $x_0$ with radius $\epsilon$
usainlightning
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Is there a questionned ordering symbol like the questionned equality?

To question the equality between $a$ and $b$ we can use $a \overset{?}{=} b$ From what I understand, the $\overset{?}{=}$ sign is to be replaced either by $=$ or $\not=$ and the writer will guide me through the process of determining wich one is…
Winks
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What's the meaning of $544/119 = 4 + 68/119$?

The Art Of Computer Programming Third Edition, page 4 While explaining Euclid's Greatest Common Divisor algorithm for the numbers $544$ and $119$, Knuth calculates the remainder of $544/119$ which is $68$ using: $544/119 = 4 + 68/119$. I don't…
sakisk
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Are subscripts 0 or 1 based?

Being a programmer by nature I can never remember when looking at a math formula if the subscript that indicates which value in a series starts at 0 or 1. I know computer arrays start at 0 so that is my instinct without thinking but noticing 0 is…
Fr33dan
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How to state each individual solution of an expression is evenly divided by n as opposed to their sum being divided by n

Given that for k2n (n=4 and k takes all integer values from 1 to n) If we want to state the sum of all solutions is evenly divisible by n we write: n ∑ k2n = 0 (mod n) k=0 Is there an equally…
John
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How to notate a vector out of a $\mathbb{R}^+$

Say you have a set $\mathbb{R}^+$, (in other words the positive real numbers), how can one express a vector with $n$ elements out of it? $\mathbb{R}^{+n}$ might by confusing and $\mathbb{R}^{n+}$ as well. Is there a quite accepted notation for this?
willeM_ Van Onsem
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Is there a symbol used to say "is well ordered by?"

For example, we know that $\Bbb N$ is well-ordered by $<$. Is there a standard way of representing this using some notation?
Cisplatin
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Express dissolved multi-summand binominal equation

After dissolving an multi summand binomial equation $$f(x)=(x_0+x_1+x_2+x_3+\ ...)^2$$ I got $n*(n-1)/2$ of these terms: $$x_0x_1+x_0x_2+x_0x_3+x_1x_2+x_1x_3+x_2x_3+\ ...$$ How do I write them in a summation formula $\sum$ or other equivalent…
Buni
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how to write it using sigma notation

I'd like to know how to create a pattern for these sum: 1) $a_{1}a_{2}a_3+a_1a_2a_4+...+a_1a_{n-1}a_n+a_2a_3a_4+a_2a_3a_5+...+ a_2a_{n-1}a_{n}+ ...+a_{n-2}a_{n-1}a_n = ?$ 2)…
Gregor
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What does -(-... mean in this equation?

I'm trying to understand what is meant by the -(-w etc. in the equation below. Can someone enlighten me? Source: Section 2.2.3 Case Amplification
conorgriffin
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A simple notation question

What does this notation $\mathbb{Z}[x]/(x^{n+1})$ mean? I guess it is a quotient group but I cannot find a precise definition. Here is the context: The cohomology ring of $\mathbb{C}P^n$ is given by…
Chromatic
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What is $\hat{\gamma}$ used in this example?

I am reading an article about support vector machine (PDF) and one part of the document the author talks about the optimal margin classifier. In the excerpt below, I do not understand why the author is switching from $\gamma$ to $ \hat{\gamma} $ …
alexandrekow
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Proportion between two intervals

Is there any way to write an equation that means the proportion between two intervals? For example, if I have the intervals [3,4] and [1,5] I would like to know the proportion between them, but I'm not sure if $\dfrac{[3,4]}{[1,5]}$ would mean that.…
user136913
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Notation query: matrix projection

I've used the following notation in a report: $G\boldsymbol{w}\in\mathcal{H}_2\,\forall\boldsymbol{w}\in\mathcal{H}_2 $ In other words $G$ projects $\boldsymbol{w}$ back into the same set. But this notation doesn't feel right. Is this correct or…
oLas
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What do vertical bars with an index mean?

A fairly basic notation question: what do the vertical bars in the following mean? x = $_{k=0}^{3}\big|\;f(k)\;\big|$ I've never seen vertical bars with an index before and I can't seem to find the answer on google either (half the problem is that I…
sjmeverett
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