User Wesley

13

20

votes

5

answers

2k

views

Why does notation for functions seem to be abused and ambiguous?

functions notation

Sep 23 at 10:15 Toby Bartels 679

5

9

votes

3

answers

209

views

$C_1$ and $C_2$ are non-crossing if they are translates of a convex disc

general-topology convex-analysis

May 14 at 12:32 Moishe Kohan 50.3k

2

8

votes

7

answers

230

views

Show that $\lim_{n \to \infty} \int_0^{\infty} \frac{1}{1+x^n}~dx = 1$

calculus integration limits convergence definite-integrals

Jul 3 at 15:54 Doug M 45.5k

4

8

votes

4

answers

197

views

Evaluate the integral $\int_0^{\infty}e^{-x} \sin x \log x ~ dx$

calculus integration definite-integrals

Jun 18 '18 at 12:06 Shashi 7,462

2

6

votes

1

answer

831

views

Pigeonhole Principle Problem

pigeonhole-principle

Apr 30 at 5:24 Dr. Mathva 4,876

2

6

votes

3

answers

121

views

Five numbers whose difference is their gcd

elementary-number-theory

Feb 20 at 6:41 FredH 3,760

1

4

votes

1

answer

55

views

Decomposing a convex quadrilateral

discrete-geometry

May 13 at 7:03 Angela Richardson 5,594

3

votes

1

answer

58

views

Infinitely many of $1,11,111,\dots$ is divisible by $2^{2019}+1$

number-theory

Apr 29 at 20:27 Robert Israel 336k

1

3

votes

1

answer

42

views

Cancelling variable factors in a rational function

rational-functions

Aug 7 '16 at 15:13 Obinna Nwakwue 801

1

3

votes

5

answers

316

views

A statement about divisibility of relatively prime integers

elementary-number-theory prime-numbers

Jul 23 '16 at 5:47 Daniel Buck 2,818

3

votes

2

answers

452

views

Zero-based numbering vs. one-based numbering for sequences

sequences-and-series

Jul 10 '16 at 17:46 Community♦ 1

3

votes

1

answer

91

views

Justification for cancelling variables in a rational expression

functions

Feb 18 '15 at 23:31 GFauxPas 4,163

1

2

votes

0

answers

58

views

Geometric mean of a sequence converges

real-analysis sequences-and-series proof-verification convergence

May 4 at 15:56 GNUSupporter 8964民主女神地下教會 14.5k

1

2

votes

3

answers

93

views

Does the equation $a^2+d^2+4=b^2+c^2$ have any solutions?

diophantine-equations

Apr 11 at 1:49 Sam 11

2

votes

2

answers

143

views

Interpreting a problem in combinatorial geometry

combinatorics euclidean-geometry

Apr 1 at 13:47 Servaes 33k

1

2

votes

1

answer

43

views

Infinite set of positive integers such that no subset sum is a square

number-theory

Mar 31 at 16:12 Μάρκος Καραμέρης 837

2

votes

3

answers

86

views

$f(n)+f(m) = q^2$ always has a solution

number-theory elementary-number-theory polynomials square-numbers

Mar 31 at 13:55 Dr. Mathva 4,876

2

votes

1

answer

39

views

Group ring isomorphic to matrix ring

matrices ring-theory group-rings ring-isomorphism

Nov 28 at 16:10 rschwieb 109k

1

2

votes

1

answer

183

views

Showing that the Dirichlet function has no limit

real-analysis limits proof-verification

Nov 21 at 5:02 астон вілла олоф мэллбэрг 41k

2

votes

3

answers

55

views

Motivation for completing the rationals and proving that x^2=2 has a real solution

real-analysis

Sep 27 '17 at 2:10 Xander Henderson 15.4k

3

2

votes

3

answers

3k

views

Why does $\ker(T) = \{0\} \Leftrightarrow T$ is injective

linear-algebra linear-transformations

Feb 27 '17 at 21:54 user326159 1,460

1

2

votes

3

answers

61

views

How to prove a formula involving polynomial sequences and their recursive representation

recurrence-relations

Nov 9 '16 at 15:15 Brian M. Scott 463k

1

2

votes

1

answer

771

views

Pulling a negative out of a square root

complex-numbers

Jan 19 '16 at 1:22 Community♦ 1

1

vote

1

answer

8

views

Volume of cone in terms of base

geometry volume

13m ago auscrypt 56

1

vote

1

answer

49

views

Packing points in a ball of radius 1, where every point is $\sqrt{2}$ apart

discrete-geometry

May 16 at 16:25 Dr. Richard Klitzing 1,830

1

vote

2

answers

40

views

Whether an area contains finitely many lattice points

geometry number-theory

Mar 28 at 1:31 Conrad 2,066

2

1

vote

2

answers

85

views

Computing $S(n,3)$, Stirling number of 2nd kind

combinatorics stirling-numbers

Mar 2 at 21:33 Mike Earnest 29.8k

1

vote

0

answers

56

views

Intersection of any 2 intervals $\implies$ all intervals intersect

proof-verification convex-geometry

Feb 24 at 16:29 Wesley 547

1

vote

1

answer

46

views

Showing an isomorphism between two quadratic rings

abstract-algebra ring-theory

Dec 9 at 2:18 Wesley 547

1

vote

0

answers

45

views

The cases in proving that a group of order 90 is not simple

abstract-algebra group-theory sylow-theory simple-groups

Dec 8 at 22:57 Wesley 547

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81 Questions

Why does notation for functions seem to be abused and ambiguous?

$C_1$ and $C_2$ are non-crossing if they are translates of a convex disc

Show that $\lim_{n \to \infty} \int_0^{\infty} \frac{1}{1+x^n}~dx = 1$

Evaluate the integral $\int_0^{\infty}e^{-x} \sin x \log x ~ dx$

Pigeonhole Principle Problem

Five numbers whose difference is their gcd

Decomposing a convex quadrilateral

Infinitely many of $1,11,111,\dots$ is divisible by $2^{2019}+1$

Cancelling variable factors in a rational function

A statement about divisibility of relatively prime integers

Zero-based numbering vs. one-based numbering for sequences

Justification for cancelling variables in a rational expression

Geometric mean of a sequence converges

Does the equation $a^2+d^2+4=b^2+c^2$ have any solutions?

Interpreting a problem in combinatorial geometry

Infinite set of positive integers such that no subset sum is a square

$f(n)+f(m) = q^2$ always has a solution

Group ring isomorphic to matrix ring

Showing that the Dirichlet function has no limit

Motivation for completing the rationals and proving that x^2=2 has a real solution

Why does $\ker(T) = \{0\} \Leftrightarrow T$ is injective

How to prove a formula involving polynomial sequences and their recursive representation

Pulling a negative out of a square root

Volume of cone in terms of base

Packing points in a ball of radius 1, where every point is $\sqrt{2}$ apart

Whether an area contains finitely many lattice points

Computing $S(n,3)$, Stirling number of 2nd kind

Intersection of any 2 intervals $\implies$ all intervals intersect

Showing an isomorphism between two quadratic rings

The cases in proving that a group of order 90 is not simple