Mathematics Stack Exchange

0

votes

0

answers

29

views

Prove that $\bar A = A' \cup A$

metric-spaces

modified 2 mins ago Daniel98 97

0

votes

0

answers

4

views

product of normally distributed random variable with discrete random variable

probability-theory stochastic-processes random-variables covariance gaussian

asked 2 mins ago Shriya 115

0

votes

1

answer

6

views

volume of a block with known are of a square inside

volume

answered 2 mins ago suhbell 81

0

votes

0

answers

8

views

Defining the residue map to prove Serre-Duality

algebraic-curves riemann-surfaces

modified 2 mins ago Something 1,789

0

votes

0

answers

2

views

The classical guass sum

galois-theory cyclotomic-fields

asked 3 mins ago Cloud JR 2,037

0

votes

0

answers

14

views

Let $m$ and $ n$ be positive integers. Prove that $\varphi(m)\varphi(n)$ is less than or equal to $\varphi(mn)$.

number-theory totient-function

modified 3 mins ago Sewer Keeper 797

0

votes

0

answers

3

views

Exponential basis for $L^2([0,\infty))$

functional-analysis fourier-analysis

asked 3 mins ago Bananach 5,656

0

votes

1

answer

4

views

Multiobjective optimization

optimization

answered 4 mins ago Zim 146

0

votes

2

answers

12

views

A Map is continuous on the inverse image of the set $(-\infty,r]$. Does this inverse image a closed set?

sequences-and-series general-topology continuity

answered 5 mins ago DanielWainfleet 43.6k

1

vote

3

answers

39

views

$\lim\limits_{x \to 0} \frac{\sin x-x}{x^2}$ without L'Hospital's rule

limits-without-lhopital

modified 5 mins ago Strictly_increasing 301

1

vote

0

answers

10

views

Description of the decomposition and the inertia group in terms of the product $\mathbb{Z}^_{p^k}\times \mathbb{Z}^_n $

number-theory galois-extensions

modified 5 mins ago Davide Motta 809

1

vote

0

answers

13

views

Computing $\int_{\textbf{R}^n} \langle x,a \rangle ^2 e^{-\frac{1}{2} \|x\| ^2}$ for some $a\in \textbf{R}^n$.

multivariable-calculus definite-integrals improper-integrals

modified 5 mins ago nanowillis 11

2

votes

1

answer

19

views

$\frac{\partial r}{\partial x} = \frac{\partial x}{\partial r} = \cos \theta$ interpretation

partial-derivative polar-coordinates

answered 6 mins ago Carlo 1,189

2

votes

1

answer

47

views

$ \mathbb{R} $ with the $ K $-topology ($ \mathbb{R}_{K} $)

general-topology

modified 6 mins ago Henno Brandsma 165k

0

votes

0

answers

2

views

Determine analytic function outside the unit circle from value of real part at the boundary.

complex-analysis functional-analysis analysis complex-numbers analytic-functions

asked 6 mins ago user69211 1

1

vote

1

answer

16

views

Algebra/number theory solution check, number of 0's at end of integer

elementary-number-theory

answered 9 mins ago fleablood 96.6k

4

votes

0

answers

30

views

Inequality involving $-x\log(x)$

calculus algebra-precalculus inequality logarithms

modified 9 mins ago Luísa Borsato 2,021

2

votes

1

answer

34

views

An Interesting Property Concerning a Sequence of Integers

sequences-and-series combinatorics discrete-mathematics

modified 10 mins ago InTheSea 141

0

votes

1

answer

16

views

Necessary and sufficient condition for $f_n$($x$) = $b_{n}x$+$c_{n}x^2$ to uniformly converge to zero

real-analysis uniform-convergence pointwise-convergence

answered 12 mins ago hamam_Abdallah 45.2k

0

votes

0

answers

5

views

Let $\sigma$ be PSD. Is it always possible to find a basis of operators $\{A_i\}_i$ such that $tr(A_i^\dagger A_i \sigma) = 0$ unless $i = j$?

linear-algebra

asked 12 mins ago user38762 69

0

votes

1

answer

12

views

If original set of vectors have zero mean, will the orthogonally projections of the vectors onto another vector have zero mean?

linear-algebra geometry projection

answered 16 mins ago mathcounterexamples.net 37.7k

2

votes

0

answers

29

views

Silly question about logs when denominator is 0

limits logarithms

modified 17 mins ago fox 783

0

votes

0

answers

4

views

Finance, find annual deposit amount when FV, PV and n is known

finance geometric-series

asked 17 mins ago banan 1

1

vote

0

answers

12

views

Length of a module over a PID

commutative-algebra

asked 17 mins ago kade 11

0

votes

1

answer

333

views

Equations solvable by Lambert Function

functions lambert-w

modified 20 mins ago IV_ 2,504

0

votes

1

answer

10

views

Is there a way to determine a function that could model the transformation of one function to another?

calculus multivariable-calculus functions

modified 22 mins ago David G. Stork 20.1k

0

votes

0

answers

7

views

Need help with getting Green's Function of operator

operator-theory boundary-value-problem greens-function

modified 26 mins ago ultram4rine 1

0

votes

0

answers

7

views

How to calculate angle in non-orthogonal system (B angle at 45 degree, C angle attached on B) based on orthogonal angles

orthogonality orthogonal-matrices

modified 29 mins ago Michael Hardy 236k

2

votes

1

answer

45

views

Is integration in high dimensions hard?

integration numerical-methods monte-carlo

modified 32 mins ago DinosaurEgg 3,526

2

votes

1

answer

10

views

Fourier Coefficients of Eisenstein Series $G_{2k}(\tau)=\sum\limits_{(m,n)\in\Bbb Z^2\setminus \{(0,0)\}}\frac{1}{(m+n\tau)^{2k}}$.

integration sequences-and-series complex-analysis analytic-number-theory modular-forms

answered 33 mins ago paul garrett 35.3k

0

votes

0

answers

2

views

Question about hyperplane based hash functions for vectors

probability-distributions vector-spaces projection

asked 35 mins ago QuestionMark 213

0

votes

1

answer

7

views

Changing reduced partial sum into a multiplicative function

number-theory

answered 36 mins ago clathratus 12.3k

1

vote

0

answers

33

views

Given the point $T$ and the line $p$, find the distance between their orthogonal projections onto the plane $\pi$.

geometry vectors analytic-geometry solution-verification

modified 36 mins ago Cheesecake 4,502

1

vote

1

answer

6

views

Does removing the “heaviest” edge of all cycles in an (unweighted) graph result in a minimum spanning tree?

graph-theory trees

modified 38 mins ago Misha Lavrov 67k

1

vote

2

answers

23

views

FTC Double Derivative of Two Integrals

calculus integration derivatives

answered 41 mins ago Carlo 1,189

1

vote

0

answers

7

views

Why do I need holomorphically immersed submanifold $M\to P^m(C)$ instead of embedding to use notion of hyperplane section bundle?

general-topology geometry differential-geometry algebraic-geometry complex-geometry

asked 43 mins ago user45765 7,459

0

votes

0

answers

27

views

Defining sine in terms of the differential equation $y''=-y$.

trigonometry soft-question definition

modified 43 mins ago Leo 2,431

8

votes

2

answers

161

views

+100

Bouncing Bullet Problem

integers python billiards

modified 47 mins ago hdighfan 426

2

votes

0

answers

22

views

Prove that the set of rapidly increasing functions is uncountable using diagonalization

discrete-mathematics elementary-set-theory solution-verification

modified 48 mins ago Aryaman Maithani 3,361

3

votes

1

answer

30

views

Why is this integral bounded?

integration analysis inequality

answered 49 mins ago csch2 2,504

2

votes

1

answer

13

views

Proof of uniqueness of Laplace Transform

proof-explanation laplace-transform

modified 51 mins ago Sahiba Arora 9,992

1

vote

1

answer

14

views

How to construct a joint pdf, other than the independent coupling, given two marginal pdf's?

probability probability-theory probability-distributions coupling

modified 52 mins ago JanTinbergen1991 236

1

vote

1

answer

21

views

Checking continuity of Rational vs irrational functions

calculus functions continuity

answered 55 mins ago Robert Israel 375k

3

votes

1

answer

13

views

What is the error of a sine function defined using a unit polygon instead of a unit circle?

geometry trigonometry polygons

answered 55 mins ago Integrand 2,949

0

votes

0

answers

9

views

Embedding of a boundary component induces isomorphism on homologies

algebraic-topology homology-cohomology cobordism

asked 55 mins ago Mihail 1,853

-1

votes

0

answers

17

views

$I, J$ ideals of a commutative ring. If $I=(a),\ \forall \, a\in I\,a \neq0_R$ then $J\subseteq I$ otherwise all elements of $J$ are zero divisors

abstract-algebra ring-theory ideals

asked 56 mins ago F.inc 949

1

vote

0

answers

15

views

What are some system of equations that cannot be solved like the quintets?

algebraic-geometry computability

asked 57 mins ago Pel de Pinda 2,109

3

votes

1

answer

31

views

First order Non-Linear ODE with no explicit form of the derivative

ordinary-differential-equations

answered 57 mins ago Professor Vector 11.6k

0

votes

1

answer

15

views

On the set $A=\{1,2,3,4,5\}$, type three such relations $a,b,c$ so that $a = a^{-1}, b = b^{-1}, c = c^{-1}$

set-theory

answered 58 mins ago Heroshizen 13

0

votes

0

answers

11

views

$f:M \to Q$ a monomorphism with $Q$ injective and $g:M \to N$ essential morphism, then there exist a mono $\bar{g}: N \to Q$ such $\bar{g} g= f$.

abstract-algebra algebraic-geometry commutative-algebra modules homological-algebra

modified 1 hour ago Cos 1,275

0

votes

0

answers

17

views

What term describes a function that treats all arguments consistently?

functions terminology binary-operations

modified 1 hour ago Bernard 149k

1

vote

0

answers

21

views

What is the degree of a polynomial in more than one variable?

polynomials terminology definition

modified 1 hour ago Xander Henderson 19.5k

1

vote

1

answer

17

views

Functions within Expectation of Brownian Motion

stochastic-processes brownian-motion

answered 1 hour ago user6247850 184

1

vote

0

answers

27

views

Convex functions and minimization

optimization convex-analysis

modified 1 hour ago Rodrigo de Azevedo 15.3k

0

votes

0

answers

12

views

Likelihood ratio test: normal for unknown variance

statistics statistical-inference hypothesis-testing

modified 1 hour ago Jhon Knows 303

1

vote

0

answers

17

views

Line intersection in $\mathbb{R}^3$

geometry

modified 1 hour ago ImHackingXD 15

10

votes

1

answer

135

views

+50

Number of zeros in difference of exponential sums: $\sum\limits_{i=1}^n a_i^x - \sum\limits_{i=1}^n b_i^x$

roots exponential-sum

modified 1 hour ago kimchi lover 18.4k

2

votes

1

answer

796

views

Hessian matrix equal to zero

multivariable-calculus

modified 1 hour ago Ernie060 4,607

0

votes

0

answers

6

views

$G$ is solvable implies there exists a chain of normal subgroups such that adjacent quotients are cyclic

abstract-algebra solution-verification solvable-groups

asked 1 hour ago bxs 85

0

votes

0

answers

4

views

Union of cone of feasible directions

elementary-set-theory convex-cone dual-cone

asked 1 hour ago measurehell 159

0

votes

0

answers

19

views

Nonexpansive Mapping Proof $(|G(x)-G(y)|<|x-y|)$

analysis inequality numerical-methods fixed-point-theorems contraction-operator

modified 1 hour ago maskenissen 1

0

votes

0

answers

5

views

m pages are printed, and the number of pages misprinted is never even. Why is any of the m-1 events $E_i =$ {misprint in the ith page} are m.i.?

probability statistics proof-explanation independence

modified 1 hour ago ensbana 993

2

votes

0

answers

26

views

Integration by parts. Push It to the Limit

integration derivatives exponential-function differential-operators

asked 1 hour ago yngabl 858

0

votes

0

answers

35

views

+50

Show that the full Fourier series of F converge pointwise to F.

partial-differential-equations fourier-analysis fourier-series pointwise-convergence

modified 1 hour ago Rodrigo de Azevedo 15.3k

0

votes

0

answers

11

views

Category of power set of a set with inclusion is Cartesian closed

category-theory adjoint-functors cartesian-closed-categories

modified 1 hour ago Arnaud D. 18.9k

0

votes

0

answers

8

views

Higher homotopy groups of a string complement in a cylinder.

algebraic-topology homotopy-theory knot-theory

modified 1 hour ago Mihail 1,853

0

votes

1

answer

12

views

Covering mappings

algebraic-topology fundamental-groups path-connected

answered 1 hour ago fish 716

1

vote

0

answers

29

views

find all pairs of natural numbers $(x, y)$ so that $121$ divides $x^2+y^2$

linear-algebra algebra-precalculus diophantine-equations

asked 1 hour ago Maria 95

0

votes

0

answers

7

views

Cardinality of Primes in UFDs over Infinite Sets

number-theory infinity unique-factorization-domains

asked 1 hour ago MSIS 336

1

vote

0

answers

21

views

Prove the following result: if $f(x) \geq g(x)$ for all $x\in I$, then $p.c.\int_{I}f \geq p.c.\int_{I}g$.

real-analysis integration solution-verification partitions-for-integration

modified 1 hour ago StubbornAtom 11.1k

1

vote

0

answers

6

views

Analytic function over an open disk

complex-analysis

asked 1 hour ago Yijie Gong 11

0

votes

0

answers

11

views

Multiple choice test in least submission attempts

combinatorics

asked 1 hour ago redteam 13

0

votes

0

answers

9

views

Matrix Operations: Name of function to rotate each column such that the first element is on the main diagonal

linear-algebra matrices

asked 1 hour ago Christopher 430

0

votes

0

answers

11

views

Is $\mathfrak{c}E$ a $C$-module for an abelian ring $C$ and an ideal $\mathfrak{c}$?

linear-algebra abstract-algebra commutative-algebra modules

asked 1 hour ago alf262 93

1

vote

0

answers

9

views

Quadratic variation of the absolute value of the Brownian motion

brownian-motion quadratic-variation

asked 1 hour ago Babado 639

2

votes

0

answers

19

views

Two convex functions equal on the natural numbers are equal

real-analysis ordinary-differential-equations analysis derivatives logarithms

asked 1 hour ago ZingZong 21

0

votes

4

answers

42

views

Let $n$ be a positive integer and $p=4n+1$, a prime number. Show that $(\frac{p-1}2)!$ is a root of $x^2+1=0$ in $\mathbb Z_p$

elementary-number-theory polynomials ring-theory

answered 1 hour ago fleablood 96.6k

0

votes

0

answers

7

views

Integral application with functions, arcs, and tangents

calculus integration functions

asked 1 hour ago qwe qwe 1

1

vote

0

answers

6

views

About convergence at no point for PDE

partial-differential-equations

asked 1 hour ago neveryield 541

-1

votes

0

answers

18

views

There are 2 lotto “6 of 49” tickets. What is probability of winning?

probability

modified 1 hour ago StubbornAtom 11.1k

1

vote

0

answers

15

views

Show that $( \nabla \times {\bf G} ) {\bf v} = \nabla \times ({\bf G}^T {\bf v})$ (curl formula)

tensors curl

asked 1 hour ago Olumide 1,083

0

votes

0

answers

8

views

Why should we minimize the sum of artificial variables in $2$ phase method?

linear-programming simplex operations-research two-phase-simplex

modified 1 hour ago Rick 830

0

votes

2

answers

48

views

How to find the $n$-th number whose sum of digits is $9$?

sequences-and-series

modified 1 hour ago herb steinberg 6,357

0

votes

0

answers

9

views

What is the moment of inertia of a thin isosceles triangular plate?

calculus integration

asked 2 hours ago Lauren Sin 359

1

vote

0

answers

24

views

about there doesn't exist a unit norm vector at a unit distance from a closed subspace.

real-analysis functional-analysis banach-spaces

modified 2 hours ago Rick 830

3

votes

2

answers

20

views

Convergence of Sequence of Indicator Functions

real-analysis convergence-divergence pointwise-convergence

modified 2 hours ago Mrcrg 528

1

vote

0

answers

20

views

Approximation of a matrix multiplication

matrices computational-mathematics symmetric-matrices

modified 2 hours ago Matías Bermann 93

3

votes

0

answers

21

views

A tangent to ellipse $E_1$ intersects ellipse $E_2$ at $P$ and $Q$. Prove that the tangents to $E_2$ at $P$ and $Q$ are perpendicular to each other.

conic-sections elliptic-curves tangent-line

asked 2 hours ago Ardent 752

1

vote

0

answers

45

views

Procedure to find explicit isomorphisms between two quotient rings: $\mathbb{R}[x]/(x^2 + 1) \cong \mathbb{R}[x]/(x^2 + \alpha^2)$

abstract-algebra ring-theory finite-fields ring-isomorphism

modified 2 hours ago user26857 41.7k

1

vote

0

answers

6

views

why if $h_{k}=f^{'}_{n_p}$ then $2\leq k\leq p$

real-analysis sequences-and-series analysis

asked 2 hours ago Karim KHAN 199

1

vote

0

answers

14

views

Finding Point In $[0,1]$ At Which $f,g$ Coincides Where $f\circ g=g\circ f$ On $[0,1]$

real-analysis calculus solution-verification rolles-theorem

asked 2 hours ago Crane1729 11

1

vote

1

answer

2

views

Self-adjoint operators on $\mathbb{C}^2$

quantum-mechanics linear-algebra

2 hours ago Dimitri 31

0

votes

0

answers

23

views

Geodesically complete translation-invariant torsion-free affine connections on $\mathbb{R}^n$

differential-geometry geodesic

modified 2 hours ago Malkoun 3,448

1

vote

0

answers

12

views

Why is the existence of periodic orbits (in triangular billiards) so hard to prove?

proof-writing dynamical-systems billiards

asked 2 hours ago Pedro 2,236

6

votes

1

answer

39

views

Sum of multinomial coefficients with bounded indices

combinatorics summation multinomial-coefficients

answered 3 hours ago metamorphy 15.2k

3

votes

0

answers

18

views

How to prove or disprove that the series are Fourier transformation for some function.

sequences-and-series functions fourier-transform

modified 4 hours ago user 1,082

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