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General Q&A about all branches of theoretical and applied mathematics, including closely-adjacent sciences where the central question is about the math.

338 posts   RSS
Activity Age Score Random
Filters (None)
66%
+2 −0
Is the nth Betti number determined by orientability?

1 answer  ·  posted 6mo ago by WheatWizard‭  ·  edited 5mo ago by WheatWizard‭

betti-numbers algebraic-topology
66%
+2 −0
Using convexity in the proof of Hölder’s inequality

1 answer  ·  posted 3mo ago by Snoopy‭  ·  last activity 23d ago by Snoopy‭

real-analysis
66%
+2 −0
The derivatives of a function at a boundary point

1 answer  ·  posted 3mo ago by tommi‭  ·  last activity 3mo ago by Snoopy‭

derivatives real-analysis
66%
+2 −0
For any real number $m$, $ \left|\sum_{n=1}^{\infty}\frac{m}{n^2+m^2}\right|<\frac{\pi}{2} $

1 answer  ·  posted 3mo ago by Snoopy‭  ·  last activity 3mo ago by Snoopy‭

calculus real-analysis
66%
+2 −0
Is it known whether most numbers are normal or not

0 answers  ·  posted 5mo ago by Grove‭

number-theory
66%
+2 −0
The purpose of logical frameworks in specifying type theories

1 answer  ·  posted 1y ago by user205‭  ·  last activity 1y ago by Derek Elkins‭

type-theory logic
66%
+2 −0
Fourier transform of an $L^1$ function is uniformly continuous

1 answer  ·  posted 3mo ago by Snoopy‭  ·  edited 3mo ago by Snoopy‭

real-analysis fourier-analysis
66%
+2 −0
Concrete examples of set theorists thinking independence proofs only determine provability rather than that a statement is neither true nor false?

1 answer  ·  posted 3mo ago by Julius H.‭  ·  last activity 3mo ago by Peter Taylor‭

set-theory
66%
+2 −0
A program which could derive theorems given formation rules in any modal logic?

1 answer  ·  posted 3mo ago by Julius H.‭  ·  edited 3mo ago by Peter Taylor‭

computational-mathematics proof-assistants
66%
+4 −1
is arithmetic finitely consistent?

0 answers  ·  posted 2mo ago by Jason‭

proof logic peano-arithmetic incompletness consistency
66%
+2 −0
matrix inverse of $I + A$ where $A$ is skew-symmetric

1 answer  ·  posted 2mo ago by Trevor‭  ·  last activity 2mo ago by Trevor‭

linear-algebra
66%
+2 −0
The Fourier transform of $1/p^3$

1 answer  ·  posted 2mo ago by C-T‭  ·  last activity 2mo ago by LL 3.14‭

complex-analysis calculus multivariable-calculus integration fourier-analysis
66%
+2 −0
Find length $MP$ in trapezoid

0 answers  ·  posted 1mo ago by TheCodidacter, or rather ACodidacter‭  ·  edited 1mo ago by TheCodidacter, or rather ACodidacter‭

geometry
66%
+2 −0
Does {7,4|3} have a realization on the Klein quartic?

0 answers  ·  posted 1mo ago by WheatWizard‭

polytopes algebraic-geometry
66%
+2 −0
On Tarski-style universes in type theory

1 answer  ·  posted 1y ago by user205‭  ·  last activity 1y ago by Derek Elkins‭

type-theory logic
66%
+2 −0
Disentangling Machine Learning Theory with Cross-Validation

0 answers  ·  posted 3y ago by seth.wagenman‭

model
66%
+2 −0
Why aren't $z_1=f(xy)$ and $z_2=f(x/y)$ functions of 2 variables?

1 answer  ·  posted 3y ago by TextKit‭  ·  last activity 3y ago by celtschk‭

calculus
66%
+2 −0
How to visualize division as splitting Dividend into B equal “partial groups”, then rounding up A partial groups to get a full group?

1 answer  ·  posted 3y ago by Chgg Clou‭  ·  last activity 3y ago by leovt‭

visualization
66%
+2 −0
In a SARIMA model, does the order in which I difference the time series matter?

0 answers  ·  posted 3y ago by anoldmaninthesea‭

statistics
66%
+2 −0
How can I deduce which operation removes redundacies?

3 answers  ·  posted 3y ago by DNB‭  ·  edited 3y ago by DNB‭

probability
66%
+2 −0
Do these major triangle lines have names?

0 answers  ·  posted 2y ago by Peter Taylor‭

euclidean-geometry triangle plane-geometry nomenclature
66%
+2 −0
Find $y=b\cos^3\theta$ and, $x=a\sin^3\theta$ from hypocycloid's formula

1 answer  ·  posted 2y ago by deleted user  ·  edited 2y ago by deleted user

calculus hypocycloid parametric-equation
66%
+2 −0
$\sum_{k=0}^{n} \binom{n}{k}=2^{n} \overset{?}{\iff} \sum_{k=0}^{n} \binom{2n+1}{k}=2^{2n}$

1 answer  ·  posted 3y ago by DNB‭  ·  edited 3y ago by DNB‭

combinatorics
62%
+3 −1
Minimal non-standard number in non-standard models of PA

1 answer  ·  posted 3mo ago by Aditya‭  ·  edited 3mo ago by The Amplitwist‭

logic model peano-arithmetic nonstandard-models
62%
+3 −1
Why are you permitted to define $1 − 1 + 1 − 1 + . . .$?

1 answer  ·  posted 3y ago by Chgg Clou‭  ·  last activity 3y ago by JRN‭

number-theory
62%
+3 −1
Why should a non-commutative operation even be called "multiplication"?

2 answers  ·  posted 3y ago by theabbie‭  ·  last activity 3y ago by celtschk‭

definition notation abstract-algebra
60%
+1 −0
proving relative lengths on a secant

1 answer  ·  posted 3y ago by msh210‭  ·  last activity 3y ago by Peter Taylor‭

euclidean-geometry
60%
+1 −0
How does Pr(an event next year) $= 1/100$ imply Pr(at least one of these events occurring in the next 25 years) $> 1/5$?

1 answer  ·  posted 3y ago by Chgg Clou‭  ·  last activity 3y ago by Nat‭

probability
60%
+1 −0
How can I re-write or supplant “basis point” UNambiguously?

0 answers  ·  posted 3y ago by Chgg Clou‭  ·  edited 2y ago by Chgg Clou‭

percentage
60%
+1 −0
If a matrix has lots of values in a column but, not in row than, what that actually called?

1 answer  ·  posted 2y ago by deleted user  ·  last activity 2y ago by 4015.alt‭

linear-algebra matrices
60%
+1 −0
differentiate under integral sign says something went wrong

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

calculus multivariable-calculus differentiation integration improper-integral
60%
+1 −0
Find the intervals on which it is increasing and those on which it is decreasing of the following function.

1 answer  ·  posted 3y ago by deleted user  ·  last activity 3y ago by deleted user

calculus derivatives real-analysis functions maxima-minima
60%
+1 −0
Prove $(\cos^3\theta+\sin^3\theta)^2= \cos^6\theta(1+\tan^3\theta)^2$

2 answers  ·  posted 2y ago by deleted user  ·  last activity 2y ago by Peter Taylor‭

trigonometry
60%
+1 −0
What it ≡ called?

1 answer  ·  posted 2y ago by Anonymous‭  ·  last activity 2y ago by Quintec‭

symbols
60%
+1 −0
What does upper indices represent?

2 answers  ·  posted 2y ago by deleted user  ·  last activity 2y ago by r~~‭

notation tensors
60%
+1 −0
Connection between caustics and conjugate points?

0 answers  ·  posted 1y ago by tommi‭

differential-geometry
60%
+1 −0
Is there a two variable quartic polynomial with two strict local minima and no other critical point?

0 answers  ·  posted 1y ago by Pavel Kocourek‭

multivariable-calculus real-analysis maxima-minima polynomials roots
60%
+1 −0
What's the common ratio for this geometric sequence?

1 answer  ·  posted 2y ago by General Sebast1an‭  ·  last activity 2y ago by tommi‭

geometric-sequence sequence
60%
+1 −0
Is there a "regular" quasi-convex function $f:\Bbb R^2 \to \Bbb R$ that is not a monotone transformation of any convex function?

0 answers  ·  posted 1y ago by Pavel Kocourek‭

multivariable-calculus real-analysis convex-analysis monotone-functions
60%
+1 −0
How's it possible to arrange 0 objects? How can 0! = 1?

3 answers  ·  posted 2y ago by DNB‭  ·  edited 2y ago by Quintec‭

combinatorics
60%
+1 −0
Are vectrices useful for calculations as opposed to formalism?

1 answer  ·  posted 2y ago by Fred Wamsley‭  ·  last activity 2y ago by Derek Elkins‭

Vectrix Numerical
60%
+1 −0
Dividing a cuboid in four

1 answer  ·  posted 1y ago by Yair Rand‭  ·  last activity 1y ago by Peter Taylor‭

geometry
60%
+1 −0
$\{f_n\}\to f$ in $X$ implies $||f||\le\liminf||f_n||$

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

real-analysis functionals normed-vector-space
60%
+1 −0
How $ijk=\sqrt{1}$?

2 answers  ·  posted 2y ago by deleted user  ·  last activity 2y ago by Tim Pederick‭

quaternions
60%
+1 −0
Obtaining the semantics of simple type theory as a particular case of the set-theoretic semantics of dependent type theory

0 answers  ·  posted 6d ago by user205‭  ·  edited 6d ago by user205‭

constructive-logic type-theory logic
60%
+1 −0
Seeking a theorem about lattices

0 answers  ·  posted 19h ago by WheatWizard‭  ·  edited 19h ago by WheatWizard‭

linear-algebra reference-request free-abelian-group
60%
+1 −0
What does it mean by saying that $C([0,1])$ is a subset of $L^\infty([0,1])$?

1 answer  ·  posted 4mo ago by Snoopy‭  ·  last activity 4mo ago by Snoopy‭

real-analysis
60%
+1 −0
$\liminf (a_n+b_n) = \liminf(a_n)+\liminf(b_n)$ provided that $\lim a_n$ exists

1 answer  ·  posted 4mo ago by Snoopy‭  ·  edited 4mo ago by Snoopy‭

real-analysis
60%
+1 −0
Why does the method of separating variables work?

0 answers  ·  posted 1mo ago by The Amplitwist‭

partial-differential-equations separation-of-variables
60%
+1 −0
Why is $ \int_0^{\infty}\left|\frac{\sin x}{x}\right|\ dx=\infty$?

1 answer  ·  posted 4mo ago by Snoopy‭  ·  last activity 4mo ago by Snoopy‭

real-analysis improper-integral
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