# Tagged Questions

Question 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.

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### If G and H are two gaphs then what does $G \Delta H$ indicate in graph theory?

I came across this notation in a book titled " Combinatorial Optimization Theory and Algorithms" by Bernhard Korte and Jens Vygen.
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### Does “Doing a thing to both sides of an equation” have a name?

A two part question. 1 True or False: when working with an equation or inequality, everything that you do is either: a substitution, or an operation performed on each side Note that algebraic or ...
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### Why are sequences and functions notated differently?

Why do we usually write, e.g., $s_n$ for sequences, while functions are usually written as $f(x)$? Conceptually, aren't sequences just functions with a subset of the naturals, not of the reals, as ...
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### Meaning of notation $L_{subscript}$ in ridge detection.

In the wikipedia article on ridge detection, it says "let $L_{pp}$ and $L_{qq}$ denote the eigenvalues of the Hessian matrix \begin{pmatrix} L_{xx} & L_{xy} \\ L_{xy} & L_{yy} \end{pmatrix}...
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### $T*T$ Notation and proof

Let $T:H\to H$ be compact where $H$ is a Hilbert space and let $T^*$ be the adjoint operator of $T$. Prove that $T^*T$ is compact and self adjoint and that the eigenvalues of $T^*T$ are nonnegative. ...
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### Visualization of residual sum of squares in matrix notation

I am trying to understand how to pass from $$RSS(\beta) = \sum_{i=1}^n (y_i - x_i^T\beta)^2$$ to RSS(\beta) = (y - X \beta)^T (y - X \beta) \end{...
### Notation for “the highest power of $p$ that divides $n$”
If $p$ is a prime and $n$ an integer, is there a standard or commonly used notation for "the highest power of $p$ that divides $n$"? It's a concept that is often used repeatedly in number-theoretic ...