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.

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How to make the distinction between $a$ is some element in $\mathbb R$ and $a$ can be any element in $\mathbb R$

This is a question relating to the notation. I think I have often seen the $a \in \mathbb R$ refer to that $a$ can be any element in $\mathbb R$. But of course, this is not necessary so, for example $a$ could be restricted to numbers 1 and 2, and…
Dole
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What does $9(9_9)$ mean?

A book claims that $9(9_9) = 9^{387420489}$. I've never seen such an expression, and I've been unable to find anything about it on Google... How is it supposed to be evaulated? For reference, the name of the book is Pasatiempos curiosos e…
kikones34
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Is there an easy way to make a plus into a minus sign when writing math on paper?

Sometimes when writing math you realize that a minus should be a plus, or vice versa. For the former, it's quite easy to convert the $-$ into a $+$. You simply need to add a vertical line through it. For a plus that you want to turn into a minus,…
Skeleton Bow
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Typography in Calculus Textbooks (or math textbooks in general)

My question is about typography in Calculus textbooks. I've scanned through numerous Calculus texts. I find that sometimes authors vary their use of "traditional" form in textbooks. For example... (I apologize for being verbose but needed to…
B flat
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Is there a mathematical symbol for unknown?

I'm searching for two symbols - considering they exist - (1) unknown value; (2) unknown probability. Note: I thought that $x$ was used in a temporary context, whenever I see it, it remains unknown until an evaluation is made. I was thinking in a…
Red Banana
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Can you help me to identify this unknown notation in his arm?

What's this in his arm? I've never seen such notation.
Red Banana
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Why don't we see a $\frac{\times}{ \div}$ like we see $\pm$?

It's common to see a plus-minus ($\pm$), for example in describing error $$ t=72 \pm 3 $$ or in the quadratic formula $$ x = \frac{-b \pm \sqrt{b^2-4ac}}{2a} $$ or identities like $$ \sin(A \pm B) = \sin(A) \cos(B) \pm \cos(A) \sin(B) $$ I've never…
Carser
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Notation for the solution to $y^y=x$.

Let $x$ be a positive real number. The solution to $y+y=x$ is written $$y=x/2.$$ The solution to $y\cdot y=x$ is written $$y=x^{1/2}.$$ Is there a notation for the solution to $y^y=x$?
user361533
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Sum with $j \ne i$

I have seen notation like this, commonly in regard to matrix multiplication: $$ b_i = \sum_{j \ne i} A_{ij} x_j $$ So this is a matrix multiplication that excludes the diagonal ($j=i$). I'm kind of confused when it's ok to just leave off…
bobobobo
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I want to write "$x,y > 0$".

I want to write "$x,y > 0$". Can I do this? Or do I have to write "$x > 0$ and $y > 0$"? Which one is the proper way to write in maths?
user349887
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What is the Psi(x) variable binding operator?

In the Free Variable article on Wikipedia, it lists these: as variable-binding operators. I have seen all of them during my math studies, except for the psi operator. What does $\psi x$ mean in this context?
Zach
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What does $]a,b[$ mean?

I recently encountered the above notation for sets, and I've never encountered it before. What does it refer to?
user41281
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Mathematical notation for 'value generated from normal distribution'

What is the correct mathematical notation for expressing that say 'x is a value generated from the given range with the probability given by normal distribution with given mu and sigma'? I am writing a pseudoalgorithm and I need to express: a = b +…
JanBed
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Typesetting the mathematical expression "const."

How do I write in the right way, that something is constant? I think, usually one does write = const., which should be an abbreviation for the Latin constat. Should I write the expression italic ($\textit{const.}$) or upright ($\textrm{const.}$)? As…
user254303
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What does $\overset \times =$ mean?

I came across this symbol on page xix of the book Universal Artificial Intelligence by Hutter: (link to full text of book) It is used for the Solomonoff-Levin universal semi-measure. I've never seen it before, and wondering if anyone can help me…
John Forbes
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