User Norbert - Mathematics Stack Exchange

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	20,396 reputation	bio	website		visits	member for	1 year, 6 months
42270 badges		location	Moscow, Russia		seen	10 mins ago

108

179

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8

answers

15

kviews

Is $dy/dx$ not a ratio?

calculus

mar 14 at 3:35 isomorphismes 845

102

176

votes

23

answers

7

kviews

Examples of apparent patterns that eventually fail

big-list examples-counterexamples

apr 10 at 3:04 Douglas B. Staple 1,026

91

131

votes

17

answers

8

kviews

Different methods to compute $\sum\limits_{n=1}^\infty \frac{1}{n^2}$

sequences-and-series complex-analysis fourier-analysis big-list faq

mar 8 at 13:57 xpaul 1

77

115

votes

28

answers

8

kviews

A challenge by R. P. Feynman: give counter-intuitive theorems that can be translated into everyday language

soft-question big-list examples-counterexamples

aug 6 at 1:40 John 1

110

106

votes

35

answers

7

kviews

Fun but serious mathematics books to gift advanced undergraduates.

reference-request soft-question big-list

feb 25 at 22:57 arielf 101

51

103

votes

18

answers

8

kviews

Nice examples of groups which are not obviously groups

abstract-algebra group-theory examples-counterexamples big-list

may 3 at 8:54 Dominic Michaelis 11.9k

26

84

votes

1

answer

2

kviews

Does the open mapping theorem imply the Baire category theorem?

functional-analysis set-theory banach-spaces axiom-of-choice baire-category

dec 10 at 23:50 Pedro Lauridsen Ribeiro 37

48

80

votes

91

answers

8

kviews

Which one result in maths has surprised you the most?

big-list

mar 8 at 20:38 Arthur Fischer♦ 21.3k

40

65

votes

6

answers

4

kviews

How can you prove that a function has no closed form integral?

calculus real-analysis integration differential-algebra

sep 19 at 17:52 Nils Matthes 1,083

32

60

votes

6

answers

1

kviews

Contest problem about convergent series

real-analysis sequences-and-series contest-math

nov 21 at 20:48 robjohn♦ 59.9k

18

52

votes

4

answers

2

kviews

Does $R[x] \cong S[x]$ imply $R \cong S$?

abstract-algebra commutative-algebra

sep 20 '11 at 2:56 Leon Lampret 2,630

29

50

votes

16

answers

2

kviews

Your favourite application of the Baire category theorem

general-topology functional-analysis big-list baire-category

apr 17 at 14:18 Seirios 8,927

32

49

votes

16

answers

8

kviews

If $AB = I$ then $BA = I$

linear-algebra matrices

may 1 at 22:19 mezhang 1,403

42

48

votes

39

answers

5

kviews

What are some examples of a mathematical result being counterintuitive?

intuition big-list

may 5 at 7:12 Gastón Burrull 1,282

34

46

votes

17

answers

4

kviews

Striking applications of integration by parts

calculus big-list

may 3 at 13:19 DepeHb 494

37

44

votes

4

answers

2

kviews

What are the Axiom of Choice and Axiom of Determinacy?

set-theory intuition axiom-of-choice

nov 26 at 11:34 Matt N. 15.3k

26

44

votes

6

answers

2

kviews

What made you choose your research field?

soft-question advice

dec 12 at 5:14 Kyle 1,485

39

44

votes

19

answers

14

kviews

Software for drawing geometry diagrams

geometry big-list math-software

may 1 at 9:49 Cruz 1

25

43

votes

10

answers

4

kviews

Complex math problem that is easy to solve

soft-question

mar 13 at 6:26 Faust7 652

14

42

votes

7

answers

2

kviews

Surprise exam paradox?

induction paradox

jan 10 '12 at 19:59 Chelonian 221

14

41

votes

3

answers

1

kviews

Is it possible for a function to be in $L^p$ for only one $p$?

real-analysis measure-theory functional-analysis banach-spaces examples-counterexamples

dec 9 '11 at 13:48 t.b. 43.2k

13

40

votes

1

answer

1

kviews

Example of a compact set that isn't the spectrum of an operator

functional-analysis banach-spaces spectral-theory

jun 2 '11 at 23:33 t.b. 43.2k

37

40

votes

26

answers

2

kviews

Big List of Fun Math Books

big-list recreational-mathematics

aug 5 at 21:30 Fred Kline 373

41

40

votes

2

answers

3

kviews

Why study Algebraic Geometry?

algebraic-geometry soft-question

jan 24 at 0:49 Javier Álvarez 4,794

17

39

votes

1

answer

1

kviews

How discontinuous can a derivative be?

real-analysis derivatives examples-counterexamples

jan 28 at 12:38 Willie Wong♦ 30.7k

14

38

votes

11

answers

1

kviews

Examples of results failing in higher dimensions

big-list education examples-counterexamples

mar 13 '12 at 3:52 Espinho da Flor 57

22

36

votes

3

answers

4

kviews

Norms Induced by Inner Products and the Parallelogram Law

functional-analysis inner-product-space norm

apr 23 at 21:09 somaye 2,003

25

35

votes

2

answers

2

kviews

Open problems in General Relativity

big-list general-relativity

aug 20 at 20:50 Community♦ 1

15

35

votes

9

answers

13

kviews

What should I learn first, Mathematica or MatLab?

math-software mathematica matlab

nov 6 at 2:50 Daniel Bittinat 21

15

35

votes

3

answers

597

views

Let $f:\mathbb{R}\longrightarrow \mathbb{R}$ a differentiable function such that $f'(x)=0$ for all $x\in\mathbb{Q}$

real-analysis

jun 26 '12 at 18:37 Squirtle 672

Norbert

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