Q&A - Mathematics

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Why does the decimal expansion of $1/(10n - 1)$ have this neat pattern?

3 answers · posted 4y ago by The Amplitwist‭ · last activity 4y ago by celtschk‭

number-theory high-school-mathematics

86%

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Complex numbers in 2D, quaternions in 4D, why nothing in 3D?

2 answers · posted 3y ago by Fred Wamsley‭ · last activity 3y ago by Derek Elkins‭

quaternions

83%

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Classification of topological points

1 answer · posted 4y ago by celtschk‭ · last activity 4y ago by Technically Natural‭

topology

83%

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Are there useful topologies on Cartesian products “in between” the product topology and the box topology?

0 answers · posted 4y ago by celtschk‭ · edited 4y ago by celtschk‭

topology

81%

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Are 3 10% chances better than one 30% chance (when penalized by a variable for failures)?

3 answers · posted 4y ago by dustytrash‭ · last activity 4y ago by Grove‭

logic basic odds

81%

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When and how should the $Z_n^2$ statistic be used?

1 answer · posted 4y ago by HDE 226868‭ · last activity 4y ago by HDE 226868‭

statistics

81%

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How can I choose a point from a uniform distribution within a regular polygon?

2 answers · posted 1y ago by Karl Knechtel‭ · last activity 1y ago by trichoplax‭

plane-geometry applied-mathematics sampling

81%

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Does this construction always give a topological vector space?

1 answer · posted 3y ago by celtschk‭ · last activity 12mo ago by JohnnyJohn‭

topology linear-algebra topological-vector-spaces

81%

+7 −0

Endomorphisms on an entropic structure whose pointwise product is the identity automorphism - entropic idempotent structure?

1 answer · posted 3y ago by Prime Mover‭ · last activity 12mo ago by Derek Elkins‭

abstract-algebra

81%

+7 −0

Prove that 49 is the only prime square to be followed by twice a prime square and then a semiprime

1 answer · posted 2y ago by Peter Taylor‭ · last activity 2y ago by Servaes‭

number-theory integer-sequences

80%

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Does there exist a non-zero game such that the sum of three or more copies of it is zero?

0 answers · posted 2y ago by celtschk‭

combinatorial-game-theory

80%

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What is the Name of Function for Probability of a Certain Sum on Random Die Rolls?

1 answer · posted 2y ago by James McLellan‭ · last activity 2y ago by Derek Elkins‭

statistics

80%

+6 −0

$g(x)\xrightarrow{x\to\infty}\infty$ Implies $g'(x)\leq g^{1+\varepsilon}(x)$

3 answers · posted 3y ago by Udi Fogiel‭ · last activity 3y ago by Peter Taylor‭

calculus

80%

+6 −0

What is special about the 11-cell and 57-cell?

1 answer · posted 2y ago by WheatWizard‭ · last activity 1y ago by ziggurism‭

polytopes

80%

+6 −0

Criteria for solvable Minesweeper game?

0 answers · posted 2y ago by Olin Lathrop‭ · edited 2y ago by Olin Lathrop‭

algorithm

80%

+6 −0

Why always rationalize a denominator?

3 answers · posted 4y ago by msh210‭ · last activity 4y ago by Derek Elkins‭

high-school-mathematics

80%

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What surface do I get by attaching $g$ handles as well as $k$ crosscaps to a sphere?

1 answer · posted 4y ago by The Amplitwist‭ · last activity 4y ago by msh210‭

geometry topology compactness connectedness sphere

80%

+6 −0

Discrete data: Graphs and skewness

2 answers · posted 4y ago by Nezar ‭ · last activity 4y ago by 1muflon1‭

skewness statistics discrete-data

80%

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Does this generalization of path-connectedness also cover general connectedness?

1 answer · posted 4y ago by celtschk‭ · last activity 10mo ago by ronno‭

topology connectedness

80%

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Computational hardness of the uniform halting problem

1 answer · posted 4y ago by user53100‭ · last activity 4y ago by Derek Elkins‭

computability oracle-turing-machine arithmetical-hierarchy

80%

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Does every divergence-free vector field arise as the curl of some vector field?

1 answer · posted 4y ago by The Amplitwist‭ · last activity 4y ago by Derek Elkins‭

geometry multivariable-calculus derivatives

80%

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How to show if a set is simply connected?

1 answer · posted 4y ago by kreijstal‭ · last activity 4y ago by Derek Elkins‭

complex-analysis

80%

+6 −0

The probability distribution of rolling $n$ dice and keeping $k$ highest

1 answer · posted 4y ago by tommi‭ · last activity 4y ago by Peter Cooper Jr.‭

probability dice

77%

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Can we adapt Furstenberg's proof of the infinitude of primes to other interesting subsets of the integers?

0 answers · posted 4y ago by HDE 226868‭ · edited 4y ago by msh210‭

number-theory topology

77%

+5 −0

Similar triangles with the same area

2 answers · posted 4y ago by msh210‭ · last activity 4y ago by DonielF‭

euclidean-geometry high-school-mathematics

77%

+5 −0

Which of the multiple definitions of correlation to use?

0 answers · posted 4y ago by Mithrandir24601‭ · last activity 4y ago by r~~‭

statistics correlation

77%

+5 −0

Normal in one base and not in another?

0 answers · posted 4y ago by Grove‭

number-theory normal bases

77%

+5 −0

What is the probability density function for the tau distribution?

2 answers · posted 1y ago by mr Tsjolder‭ · last activity 10mo ago by Michael Hardy‭

statistics distributions

77%

+5 −0

Finding a single row of Matrix after exponentiation

1 answer · posted 2y ago by theabbie‭ · edited 2y ago by trichoplax‭

exponent algorithm matrices

77%

+5 −0

Notation for one-sided hypothesis testing

1 answer · posted 3y ago by tommi‭ · last activity 1y ago by Glen_b‭

statistics notation hypothesis-testing

77%

+5 −0

Why can't we conclude the extrema property of a function from its quadratic approximation when the discriminant is zero?

1 answer · posted 2y ago by Snoopy‭ · last activity 2y ago by Snoopy‭

multivariable-calculus derivatives

77%

+5 −0

Is $f(x)=\sin(x)$ the unique function satisfying $f'(0)=1$ and $f^{(n)}(\Bbb R)\subset [-1,1]$ for all $n=0,1,\ldots$?

1 answer · posted 2y ago by Grove‭ · edited 2y ago by Pavel Kocourek‭

derivatives real-analysis

77%

+5 −0

How to find perfect squares such that their base 9 representation is all 1s?

1 answer · posted 1y ago by CrSb0001‭ · last activity 1y ago by Lisanne‭

number-theory bases recreational-mathematics

77%

+5 −0

Getting backward of partial differentiation's chain rule

3 answers · posted 3y ago by deleted user · last activity 3y ago by Derek Elkins‭

multivariable-calculus differentiation chain-rule

77%

+5 −0

Finding the smallest Mersenne-number multiple of an odd integer

1 answer · posted 4y ago by wizzwizz4‭ · last activity 4y ago by Peter Taylor‭

binary mersenne-numbers algorithm factoring

75%

+4 −0

What is the probability that the convex hull of $n$ randomly distributed points has $l$ of the points on its boundary?

1 answer · posted 2y ago by siric‭ · edited 2y ago by tommi‭

probability convex-hull

75%

+4 −0

Are we in a "history-valley" for Topology?

2 answers · posted 3y ago by whybecause‭ · last activity 3y ago by Derek Elkins‭

topology history-philosophy-of-math

75%

+4 −0

Optimising a 3 value problem (well 2 really)

1 answer · posted 3y ago by KalleMP‭ · last activity 3y ago by Peter Taylor‭

analysis formula algorithm

75%

+4 −0

$\int_{E_n} |g|^q = \left| \int_E \chi_{E_n}\cdot \text{sgn}(g)\cdot g \cdot |g|^{q-1}\cdot |g| \right|$

0 answers · posted 3y ago by whybecause‭ · edited 3y ago by Derek Elkins‭

real-analysis Lp-space

75%

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If $\mathbf{R}$ is thought of as a vector space over $\mathbf{Q}$, what is its dimension?

1 answer · posted 2y ago by Snoopy‭ · last activity 2y ago by r~~‭

linear-algebra vector-space

75%

+4 −0

Proving that $p\mid (p+1776)$ if $p$ is a prime and $p(p+1776)$ is a perfect square

2 answers · posted 2y ago by Snoopy‭ · last activity 2y ago by Snoopy‭

number-theory algebra

75%

+4 −0

Missing a solution: Are A and B always equal if A-B=0

3 answers · posted 3y ago by re89j‭ · last activity 3y ago by tommi‭

logic equation algebra problem

75%

+4 −0

Is it impossible to prove Jensen's inequality by way of step functions?

1 answer · posted 3y ago by whybecause‭ · last activity 3y ago by whybecause‭

real-analysis convex-analysis Jensen's-inequality

75%

+4 −0

Generalization of categorical product

1 answer · posted 2y ago by r~~‭ · last activity 2y ago by Derek Elkins‭

category-theory

75%

+4 −0

Is this formula for the minimal sum correct?

1 answer · posted 2y ago by celtschk‭ · last activity 2y ago by celtschk‭

set-theory ordinal-numbers

75%

+4 −0

Intuitively, why's X% of Y = Y% of X?

1 answer · posted 4y ago by Chgg Clou‭ · last activity 4y ago by celtschk‭

percentage

75%

+4 −0

Given a triangle with squares on two sides, the line segments joining the centres of the squares to the midpoint of the third side are equal and perpendicular

1 answer · posted 4y ago by The Amplitwist‭ · edited 4y ago by ArtOfCode‭

geometry complex-analysis

75%

+4 −0

Product of empty set of elements vs. product over empty indexing set — is there any difference?

1 answer · posted 4y ago by The Amplitwist‭ · edited 2y ago by Peter Taylor‭

product definition notation algebra

75%

+4 −0

Is this topology basis dependent?

1 answer · posted 4y ago by celtschk‭ · last activity 4y ago by Incnis Mrsi‭

topology linear-algebra topological-vector-spaces

75%

+4 −0

In $P(X\leq q)$, what do we call $q$?

1 answer · posted 4y ago by anoldmaninthesea‭ · last activity 4y ago by gramps‭

probability

Communities