User Hagen von Eitzen

359 votes

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How can a piece of A4 paper be folded in exactly three equal parts?

answered Apr 2, 2014 at 9:48

243 votes

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Why is empty set an open set?

answered Jul 19, 2013 at 6:10

175 votes

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Can you be 1/12th Cherokee?

answered Jan 18, 2015 at 19:18

102 votes

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Why do people lose in chess?

answered Jul 7, 2014 at 17:12

100 votes

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What exactly are eigen-things?

answered Feb 11, 2013 at 10:56

98 votes

How do I convince my students that the choice of variable of integration is irrelevant?

answered Jan 21, 2014 at 14:37

96 votes

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Why is the determinant the volume of a parallelepiped in any dimensions?

answered Jun 23, 2013 at 13:35

91 votes

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How to prove that a $3 \times 3$ Magic Square must have $5$ in its middle cell?

answered Jan 13, 2014 at 7:27

85 votes

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Can two figures have the same area, perimeter, and same number of segments have different shape?

answered Jul 25, 2019 at 5:56

78 votes

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What's so special about characteristic 2?

answered Dec 13, 2015 at 9:09

77 votes

How can one prove that $e<\pi$?

answered Sep 10, 2013 at 16:25

75 votes

Irreducible polynomial which is reducible modulo every prime

answered Apr 17, 2016 at 15:00

72 votes

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How can I answer this Putnam question more rigorously?

answered Jul 28, 2016 at 18:04

67 votes

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Largest prime number with all digits different

answered Oct 25, 2014 at 14:00

66 votes

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Quickest way to determine a polynomial with positive integer coefficients

answered Jul 17, 2013 at 21:59

65 votes

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Why do the French count so strangely?

answered May 14, 2013 at 10:06

61 votes

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Are there any Mersenne primes, besides 3, that end in 3

answered Aug 13, 2015 at 15:59

58 votes

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Property of 111,111

answered Dec 27, 2015 at 22:42

54 votes

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Why is $\varphi$ called "the most irrational number"?

answered May 18, 2013 at 23:17

53 votes

How can you show Godel's incompleteness theorem using mathematical symbols?

answered Jun 2, 2015 at 14:21

53 votes

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Cover of "Gödel, Escher, Bach"

answered Aug 10, 2017 at 20:15

52 votes

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counting the number of elements in a conjugacy class of $S_n$

answered Jul 21, 2013 at 21:49

51 votes

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Nested radicals of 1000 square roots

answered Feb 9, 2015 at 12:15

50 votes

Why are continuous functions not dense in $L^\infty$?

answered Oct 25, 2012 at 19:54

49 votes

Can every proof by contradiction also be shown without contradiction?

answered Nov 24, 2012 at 15:49

49 votes

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Rigour in mathematics

answered Aug 11, 2013 at 17:22

48 votes

Do we have negative prime numbers?

answered Nov 2, 2014 at 12:33

46 votes

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If a group $G$ has odd order, then the square function is injective.

answered Oct 11, 2013 at 6:08

45 votes

Show that a nonabelian group must have at least five distinct elements

answered Oct 16, 2016 at 15:40

43 votes

Why is $1 - \frac{1}{1 - \frac{1}{1 - \ldots}}$ not real?

answered Mar 4, 2016 at 17:29

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11,550 Answers

How can a piece of A4 paper be folded in exactly three equal parts?

Why is empty set an open set?

Can you be 1/12th Cherokee?

Why do people lose in chess?

What exactly are eigen-things?

How do I convince my students that the choice of variable of integration is irrelevant?

Why is the determinant the volume of a parallelepiped in any dimensions?

How to prove that a $3 \times 3$ Magic Square must have $5$ in its middle cell?

Can two figures have the same area, perimeter, and same number of segments have different shape?

What's so special about characteristic 2?

How can one prove that $e<\pi$?

Irreducible polynomial which is reducible modulo every prime

How can I answer this Putnam question more rigorously?

Largest prime number with all digits different

Quickest way to determine a polynomial with positive integer coefficients

Why do the French count so strangely?

Are there any Mersenne primes, besides 3, that end in 3

Property of 111,111

Why is $\varphi$ called "the most irrational number"?

How can you show Godel's incompleteness theorem using mathematical symbols?

Cover of "Gödel, Escher, Bach"

counting the number of elements in a conjugacy class of $S_n$

Nested radicals of 1000 square roots

Why are continuous functions not dense in $L^\infty$?

Can every proof by contradiction also be shown without contradiction?

Rigour in mathematics

Do we have negative prime numbers?

If a group $G$ has odd order, then the square function is injective.

Show that a nonabelian group must have at least five distinct elements

Why is $1 - \frac{1}{1 - \frac{1}{1 - \ldots}}$ not real?