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Good Question

Question score of 25 or more. This badge can be awarded multiple times.

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Proving that every isometry of $\mathbb{R}^n$ is of the form of a composition of at most $n+1$ reflections

Awarded Sep 22 at 13:24

Belgi

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Perfect Map $p:\ X\to Y$, $Y$ compact implies $X$ compact

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KarlG

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Non-trivial zero(s) of Akiyama-Tanigawa triangle

Awarded Sep 20 at 0:09

Integrand

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Is the Collatz conjecture in $\Sigma_1 / \Pi_1$?

Awarded Sep 18 at 22:35

Steven Stadnicki

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What would a base $\pi$ number system look like?

Awarded Sep 17 at 20:05

Luke Machowski

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Dirac delta in polar coordinates

Awarded Sep 14 at 14:56

JFNJr

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Mickey Mouse Polygon - Regular Polygons forming Mysterious Angle

Awarded Sep 14 at 14:09

Chris So

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The law of the unconscious statistician

Awarded Sep 13 at 13:11

Jori

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Is $a_1\cdots a_n + \frac1{a_1\cdots a_n}$ a polynomial in $a_i + \frac1{a_{i+1}}$?

Awarded Sep 12 at 16:01

tenth

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Fewest steps to reach $200$ from $1$ using only $+1$ and $×2$

Awarded Sep 11 at 9:09

jeremy radcliff

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What is an algebraic variety?

Awarded Sep 10 at 18:00

Nico

1,65315 silver badges24 bronze badges

smooth functions or continuous

Awarded Sep 9 at 15:58

Rosa

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What is a Theta Function?

Awarded Sep 8 at 14:32

bolbteppa

4,6394 gold badges34 silver badges64 bronze badges

Seeking a closed form for the sequence $a_n=\frac{a_{n-1}+a_{n-2}}{a_{n-1}-a_{n-2}}$, with $a_0=1$ and $a_1= 2$

Awarded Sep 6 at 19:55

Bryle Morga

1,2696 silver badges18 bronze badges

Compact sets as point spectrum of a bounded operator

Awarded Sep 4 at 15:13

Theo

2,35515 silver badges23 bronze badges

What is the intuition behind the concept of Tate twists?

Awarded Sep 2 at 7:07

Nicole

2,59320 silver badges22 bronze badges

Does there exist a real-valued function that satisfies $f(x) = \sum_{n=1}^{\infty} \frac{x^n}{f(n)}$ for all real $x$?

Awarded Aug 30 at 11:10

Kraken

7635 silver badges15 bronze badges

Evaluating the product $\prod\limits_{k=1}^{n}\cos\left(\frac{k\pi}{n}\right)$

Awarded Aug 28 at 0:05

Cody

14.5k40 silver badges104 bronze badges

Events in the tail $\sigma$-algebra

Awarded Aug 26 at 21:39

Ant

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Can $\ln$ be written as a ratio of polynomials?

Awarded Aug 26 at 4:24

aqualubix

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Why this approximation for $\pi$ is so accurate?

Awarded Aug 25 at 14:14

JWalter

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How Entropy scales with sample size

Awarded Aug 22 at 12:04

Nathaniel Bubis

33.6k10 gold badges88 silver badges147 bronze badges

On the integral $\Re \left\{\int _0^{\infty }\frac{\arctan ^2\left(x\right)\operatorname{arctanh} \left(x^2\right)}{x}\:dx\right\}=G^2$

Awarded Aug 22 at 11:32

Jorge Layja

Do we know of an explicit real number that is not in the set produced by the convergent rational series?

Awarded Aug 21 at 17:49

Resu

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Smallest non-commutative ring with unity

Awarded Aug 18 at 17:13

pardis

2851 gold badge3 silver badges4 bronze badges

IMO 1988, problem 6

Awarded Aug 17 at 12:34

Mikael Jensen

1,8972 gold badges18 silver badges26 bronze badges

Does it make sense to learn mathematical concepts as you encounter them rather than in a fixed progression? [closed]

Awarded Aug 17 at 8:47

Thor Ether

3632 silver badges7 bronze badges

Supremum of Infimum and Infimum of Supremum

Awarded Aug 17 at 3:05

JohanLiebert

1,2272 gold badges18 silver badges28 bronze badges

Why do these two lines have the same probability of intersecting the circle?

Awarded Aug 16 at 15:35

Dan

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Does the sum of reciprocals of all prime-prefix-free numbers converge?

Awarded Aug 15 at 13:07

Dan Brumleve

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Differentiation under the integral sign for Lebesgue integrable derivative

Awarded Aug 14 at 20:51

Sam

16.5k2 gold badges61 silver badges113 bronze badges

Show that $\operatorname{rank}(A+B) \leq \operatorname{rank}(A) + \operatorname{rank}(B)$

Awarded Aug 14 at 10:51

xenon

3,52812 gold badges43 silver badges52 bronze badges

Why does trying to compute $\lim_{x\to-\infty} {2x-1\over \sqrt{3x^2+x+1}}$ result in the negative of the answer given?

Awarded Aug 14 at 8:45

Cdizzle

6014 silver badges12 bronze badges

How to use AND condition in Desmos [closed]

Awarded Aug 12 at 18:48

pajczur

5331 gold badge6 silver badges11 bronze badges

Measurability of one Random Variable with respect to Another

Awarded Aug 12 at 13:45

duckworthd

1,1551 gold badge14 silver badges21 bronze badges

Solution to integral $\int \frac{1}{x-x \, \text{cot}(x)+1} \, dx$

Awarded Aug 8 at 18:26

EmFed

5293 silver badges13 bronze badges

What is the idea behind distributions?

Awarded Aug 7 at 18:09

Denis

1,2034 silver badges13 bronze badges

Is the set of points in $\mathbb R^3$ with exactly one rational coordinate connected?

Awarded Aug 6 at 14:45

Derivative

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Sequence of monotone functions converging to a continuous limit, is the convergence uniform?

Awarded Aug 5 at 20:31

BlueBuck

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Does $y''''=y^{2019}$ have a solution defined on $\mathbb R$ and not identically equal to zero?

Awarded Aug 5 at 9:34

pioo

5932 silver badges13 bronze badges

Does the order, lattice of subgroups, and lattice of factor groups, uniquely determine a group up to isomorphism?

Awarded Aug 4 at 16:51

tomas.lang

5096 silver badges10 bronze badges

Is equality the same as identity?

Awarded Aug 3 at 5:48

DrStrangeLove

8511 gold badge12 silver badges18 bronze badges

Concrete Problems that can be solved by appealing to a Moduli Space

Awarded Aug 2 at 23:18

Andres Mejia

21.7k2 gold badges35 silver badges68 bronze badges

Gradient and Jacobian row and column conventions

Awarded Aug 2 at 19:57

Flash

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Are these theorems about squares known?

Awarded Aug 2 at 13:52

زكريا حسناوي

4,4619 silver badges25 bronze badges

Asymptotics of $a_n$ such that $n^2(a_{n+1}-2a_n+a_{n-1})=\lambda a_n$

Awarded Aug 1 at 5:01

metamorphy

44.3k16 gold badges63 silver badges145 bronze badges

Which is greater, $20 \uparrow\uparrow\uparrow\uparrow 20$ or $4 \uparrow\uparrow\uparrow\uparrow\uparrow 4$?

Awarded Aug 1 at 0:03

El'endia Starman

4,0961 gold badge30 silver badges46 bronze badges

Prove that Every Vector Space Has a Basis

Awarded Jul 31 at 19:23

Andy Tam

3,5876 gold badges37 silver badges58 bronze badges

Proof that the cross product is not associative without using components

Awarded Jul 31 at 16:07

Username Unknown

4,8439 gold badges62 silver badges113 bronze badges

Concrete examples and computations in differential geometry

Awarded Jul 29 at 4:11

Saal Hardali

5,0993 gold badges37 silver badges87 bronze badges

Evaluating the infinite product $\prod\limits_{k=2}^\infty \left ( 1-\frac1{k^2}\right)$

Awarded Jul 28 at 3:05

Sherloek holmes

5374 silver badges8 bronze badges

For what values of $n$ can coins of radius $\frac12,\frac13,\frac14,...,\frac1n$ be held rigidly in a circular tray of radius $1$?

Awarded Jul 28 at 2:48

Dan

40.3k5 gold badges83 silver badges247 bronze badges

Prove $ \int_0^1 \frac{\ln^a(1-x)\ln(1+x)}{x}dx=(-1)^a a! \sum_{n=1}^\infty\frac{H_n^{(a+1)}}{n2^n}$

Awarded Jul 26 at 12:42

Ali Olaikhan

28.2k4 gold badges68 silver badges151 bronze badges

More direct proof that $ \int_0^\infty\frac{\tanh(a x)}{\tanh(\pi x)}\sin(2ax^2)\,dx=\frac{1}{4}$ is independent of parameter $a$

Awarded Jul 26 at 12:05

D.B. Cooper

4,0202 gold badges28 silver badges62 bronze badges

A regular $n$-gon contains a regular $(n+1)$-gon, with no sides coinciding. What is the maximum number of points of contact between them?

Awarded Jul 24 at 22:45

Dan

40.3k5 gold badges83 silver badges247 bronze badges

Why is "h" used for entropy?

Awarded Jul 24 at 16:01

Quinn Culver

4,6792 gold badges31 silver badges51 bronze badges

Why does this work? Applying residue theorem to some functions with non-integer powers in the denominator. Surprisingly it yielded the correct result [closed]

Awarded Jul 23 at 21:37

Egor Zaytsev

2611 silver badge11 bronze badges

On the invertibility of the adjacency matrix of a graph

Awarded Jul 21 at 19:32

the_candyman

14.3k4 gold badges38 silver badges67 bronze badges

'Does not necessarily equal' symbol

Awarded Jul 21 at 15:03

AJMansfield

1,0531 gold badge8 silver badges23 bronze badges

What does the word "let" mean in mathematics?

Awarded Jul 21 at 2:30

Qiaochu Yuan

477k55 gold badges1.1k silver badges1.5k bronze badges

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