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Interesting 9 Bountied Hot Week Month
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1 answer
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Exercise 10 of chapter 1 of Rudin's Functional Analysis

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Toby Bartels
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0 answers
8 views

Expected value of $(X-Y)sgn(A-B+X-Y)$

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Hepdrey
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0 answers
18 views

Constructing a group $(G, \Delta)$ isomorphic to $(G, \ast)$.

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The Rizzler
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19 votes
6 answers
2k views

Closed form of $\int_{0}^{\pi/2} \tan^{-1} \left( \frac{\cos x}{\sin x - 1 - \sqrt{2}} \right) \tan x\;dx$

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Quanto
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1 vote
3 answers
102 views

Find the limit $\lim_{n\to \infty} \sum_{k=1}^{n} \sqrt{1+\frac{k}{n^2}}-1$

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zeta2
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0 votes
0 answers
13 views

Is it true that $p_n$ does not divide $4n^2-5$?

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John
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2 votes
2 answers
226 views

Upper bound on the commute time for adjacent nodes

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minh quý lê
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16 votes
1 answer
400 views
+50

Is the Collatz map algorithmically decidable?

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Игорь
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2 votes
1 answer
141 views

Can we simplify the alternating sum $\sum_{i=0}^{n}(-1)^{i}{{n+i}\choose{i}}$?

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RobPratt
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2 votes
2 answers
173 views

What is the largest integer $d$ such there is a congruence relation on primes p so that $x^2 + dy^2 = p^2$ has a non-zero integral solution?

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Will Jagy
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0 answers
9 views

Invariant trees of outer automorphism of free groups

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quuuuuin
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2 answers
101 views

Domain and range of $f(x)=\frac{\sqrt{x-5}}{\sqrt{3-x}}$ — is the domain empty or not?

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Vikram
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1 vote
1 answer
771 views

What is the probability of getting STRAIGHT FLUSH in a $13$-card poker game?

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CommunityBot
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2 votes
1 answer
41 views

Is there a construction of the Everywhere doubled line for which homogeneity is apparent in the representation?

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Noah Schweber
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58 votes
0 answers
2k views

Does there exist a polynomial $P(x,y)$ which detects all non-squares?

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T﹏T
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1 vote
0 answers
24 views

Strict monotone differences of analytic functions

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MathQueen
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0 answers
57 views

Using self-adjoint operator to define Euclidean norm

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jayant
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2 votes
1 answer
93 views

Simple real life problem and reasoning

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StephenP
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0 votes
1 answer
774 views

How to show a polyhedral is non-empty?

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4 votes
0 answers
90 views

A $3$-adic valuation regarding $ C_n = \frac{1}{3+\frac{2}{5+\frac{3}{7+\frac{4}{11+\frac{5}{13+\dots\frac{n}{p_n}}}}}} $ is always $1$?

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mezzoctane
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1 vote
0 answers
36 views

Closure operator over simplicial complex

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Alma Arjuna
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5 votes
1 answer
110 views

Does the closest root of a n-th partial sum of a power series to a root of the power series converge?

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Torsten Schoeneberg
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1 vote
0 answers
87 views

Equivalent definitions of vector-valued Riemann integral

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WillG
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2 answers
38 views

Relationship between distance from chords and distance to tangent

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SRobertJames
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1 vote
1 answer
777 views

Why do you subtract 1 in a leap year if the date falls before March?

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0 votes
0 answers
37 views
+100

Solving for a diffraction grating's orientation and surface periodicity from its diffracted beams, can the problem be inverted?

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uhoh
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2 votes
0 answers
255 views

Why are normal numbers important?

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Alessandro Falconi
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0 answers
12 views

Question on controlling norm of output of a semidefinite operator by inner product

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ununhappy
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9 votes
3 answers
546 views

Is Fodor's Lemma necessary for the $\omega_1$ train station puzzle?

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Elliot Glazer
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12 votes
1 answer
860 views

Is there any known application for normal numbers?

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Alessandro Falconi
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3 votes
0 answers
73 views

Most general Logarithm of a matrix

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Ben Grossmann
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4 votes
3 answers
266 views

Find all real solutions $(x_1,\dots,x_n)\in\mathbb{R}^n$.

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Ataulfo
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6 votes
1 answer
803 views

extension of valuation rings

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CommunityBot
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20 votes
2 answers
704 views

How far can an infinite number of unit length planks bridge a right-angled gap?

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The Guy with The Hat
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0 votes
0 answers
22 views

Loci of sliding ellipse foci

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Narasimham
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0 votes
0 answers
42 views

approximation formula like Stirling’s for factorial for the number of Dispositions

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Alessandro Falconi
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1 vote
1 answer
44 views

The least positive integer ending in $7$ which quintuples if the $7$ is moved to the front

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Greg Martin
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0 votes
2 answers
74 views

Prove $V\otimes W \cong \mathcal{L}(V^*,W^*;\mathbb{K})$

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azif00
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1 vote
1 answer
39 views

How to show that the ratio test for $\sum_{n=1}^\infty\frac{(-1)^n\sqrt{n^2+1}}{n\ln n}$ is unity?

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匚ㄖㄥᗪ乇ᗪ
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-2 votes
0 answers
39 views

Topological Representations of Bipartite Qubit States from a new perspective

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David Gao
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0 votes
0 answers
7 views

Relating Parameters of an Autoregressive Model Back to Physical Parameters of its Equivalent Differential Equation

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Jordan McBain
  • 133
-1 votes
1 answer
53 views

Rotating a unit vector to another vector using two consecutive axes

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Andrei
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1 vote
1 answer
778 views

How to partition a set of positive integers as evenly as possible?

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CommunityBot
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0 votes
4 answers
155 views

What is the length of the height AH?

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Blue
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11 votes
3 answers
4k views

Show harmonic function is constant on $\mathbb{R}^n$

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K.defaoite
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0 votes
1 answer
41 views

Terminology confusion regarding quotient topological spaces

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Aniruda Suswaram
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7 votes
2 answers
195 views

Find $\sum\limits_{i,j,n\ge1}\frac{n + j + i}{n j i (n + j)(n + i)(j + i)}$

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RobPratt
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1 vote
2 answers
799 views

computing volume of unit ball in n-dimensions using polar coordinates

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RobPratt
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3 votes
2 answers
246 views

How does the Black-Scholes equation handle drift?

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Markus Klyver
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0 votes
2 answers
131 views

A Consequence from Grauert's Result on Cohomology of Fibres

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user267839
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0 answers
21 views

Why Fourier sine series of $F(x,t)$ is $\sum_{n=1}^{\infty}b_n(t)\sin(\frac{n\pi}l x)$ with $b_n(t)=\frac2l \int_{s=0}^l F(s,t)\sin(\frac{n\pi}ls)ds$?

User's user avatar
User
  • 8,477
3 votes
2 answers
808 views

Classifying space of a category / classifying space of a group

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Dennis
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0 votes
1 answer
982 views

An example of outer measure.

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CommunityBot
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8 votes
3 answers
6k views

Why is Rationals w.r.t addition not an Isomorphism to Rationals w.r.t. multiplication?

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Lee Mosher
  • 138k
7 votes
1 answer
204 views

Exponential of monos over terminal object

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Alessandro
  • 2,846
1 vote
1 answer
71 views

Clarification about pair homotopies

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Alessandro
  • 2,846
1 vote
1 answer
282 views

I need a $T_D$ topological space that is not sober

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Alessandro
  • 2,846
3 votes
0 answers
118 views

Sheaves on the finest Grothendieck topology

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Alessandro
  • 2,846
0 votes
0 answers
40 views

Proving the solution of heat equation is $C^2_1(\mathbb R^n \times (0,\infty))$

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K.defaoite
  • 14.4k
0 votes
1 answer
138 views

When is the pullback functor monadic

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Alessandro
  • 2,846
2 votes
0 answers
41 views

Expressing function in terms of preferred variables

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Daniele Tampieri
  • 11k
3 votes
1 answer
61 views

Can We Prove the Completeness of Propositional Logic also with Structural Induction?

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Tankut Beygu
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1 vote
1 answer
783 views

Is an open interval (in one-dimensional R) a strictly convex set?

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CommunityBot
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6 votes
3 answers
13k views

Calculation of expectation of inverse of a chi-square RV

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BoiBhai
  • 158
1 vote
1 answer
47 views

Why are the projection functors in the definition of the product of categories explicitly defined?

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Nicholas Todoroff
  • 10.6k
7 votes
0 answers
100 views

Help with $\int_{0}^{\pi /4} x^3 (\sqrt{\tan (x)} + \sqrt{\cot (x)}) dx$

Prem's user avatar
Prem
  • 15.7k
0 votes
1 answer
23 views

examples of quantification over mixed predicates in a concrete third or higher logic theory

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Noah Schweber
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0 votes
1 answer
35 views

Necessary and sufficient conditions for the theory of a quotient model to be equal to the theory of the main model

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Noah Schweber
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1 vote
0 answers
99 views

How to extend series coefficient for negative coefficients?

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John C
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2 votes
1 answer
32 views

Approximate set of finite Lebesgue measure by finite union of open intervals

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Emptyset
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0 answers
22 views

Why does $\lim_{x \to 0}a_n = -C_n(g(1/x))$?

John C's user avatar
John C
  • 127
0 votes
0 answers
27 views

Can we apply the principle of superposition on the initial condition for a P.D.E.?

User's user avatar
User
  • 8,477
0 votes
2 answers
38 views

Having problem understanding the answer to the $1$D Heat Equation with the initial condition $U(x,0)=u_0-u_0\sin x$

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User
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2 votes
0 answers
28 views

Understanding the Borel-Stieltjes measure

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hdecristo
  • 1,241
0 votes
0 answers
32 views

Is a division ring with a compatible total order, necessarily commutative?

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rayaisu
  • 23
5 votes
1 answer
496 views

Is there a combinatorial proof that the Catalan number $C_n$ satisfies $(n+1)C_n={2n \choose n}$?

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Dean Rubine
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3 votes
1 answer
71 views

Finding a function for $\sin(x)\sec(y) = \sin(y) + \sec(x)$

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Thành Nguyễn
  • 3,755
2 votes
0 answers
28 views

Vector bundles with equivalent sphere bundles

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user39598
  • 1,711
2 votes
2 answers
1k views

The Best Prize Problem

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Nguyen Dang Son
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1 vote
0 answers
23 views

Is there a dense set of Lipschitz functions on the unit ball which all peak at the same point on the boundary?

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user122916
  • 1,237
0 votes
1 answer
785 views

Fourier Integral Theorem?

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CommunityBot
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3 votes
0 answers
185 views

Is there any mathematical theory that is isomorphic to its metatheory?

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Tankut Beygu
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0 votes
1 answer
788 views

An Introduction to Theory of Groups by Joseph J. Rotman - Exercise 2.21 - (ii)

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CommunityBot
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0 answers
23 views

Supremum of Subsheaves

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Itserpol
  • 543
0 votes
0 answers
29 views

Computing Composition Factor Multiplicities of the Verma Module $M(0)$ for $\mathfrak{sl}_3$

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Gyh
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2 votes
0 answers
48 views

Stalks of quotient of ringed topological space are local

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user128787
  • 1,344
3 votes
3 answers
243 views

IMO $2024$ Problem $4$ (Using Method of Moving Points)

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Ak3.14
  • 453
3 votes
1 answer
98 views

Why is fact that the determinant of this matrix is 0 equivalent to $x'^T Fx=0$

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Rodrigo de Azevedo
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8 votes
1 answer
118 views

The numerator of $ C_{n>4} = \frac{1}{3+\frac{5}{7+\frac{11}{13+\frac{17}{19+\frac{23}{29+\dots p_n}}}}} $ is always divisible by $17$?

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Thinh Dinh
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1 vote
0 answers
24 views

Is there a deconvolution of two Gaussians, which conserves area?

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Gustamons
  • 91
0 votes
2 answers
9k views

Find all the units and zero-divisors of $\Bbb Z_{15}$

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Moinsdeuxcat
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1 vote
1 answer
80 views

Must $g(4)$ satisfy any inequality if only $g(1)$, $g'(1)$, and $g''(1)$ are known?

Paul Frost's user avatar
Paul Frost
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1 vote
1 answer
97 views

Finding Limits and Determining Uniform Convergence

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Anne Bauval
  • 51.2k
0 votes
1 answer
69 views

Doubt in derivation for distance between two points in three dimensions

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Nate
  • 313
5 votes
4 answers
749 views

What makes higher/second-order logic incompatible with completeness theorem?

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Noah Schweber
  • 265k
2 votes
2 answers
422 views

Constructing the binary Golay code

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Flint
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