User nullgeppetto

1211 votes

26 answers

127k views

Is $\frac{\textrm{d}y}{\textrm{d}x}$ not a ratio?

BBSysDyn

15.1k

asked Feb 9, 2011 at 16:23

792 votes

1 answer

43k views

A proof for $\dim(R[T])=\dim(R)+1$ without prime ideals?

ring-theory commutative-algebra noetherian krull-dimension dimension-theory-algebra

Martin Brandenburg

148k

asked Apr 11, 2013 at 15:19

738 votes

12 answers

209k views

Does $\pi$ contain all possible number combinations?

number-theory irrational-numbers pi

Chani

7,381

asked Oct 18, 2012 at 14:35

369 votes

71 answers

79k views

'Obvious' theorems that are actually false

soft-question big-list

beep-boop

11.1k

asked Jun 4, 2014 at 17:38

340 votes

11 answers

211k views

What is the importance of eigenvalues/eigenvectors?

linear-algebra soft-question eigenvalues-eigenvectors

Ryan

5,129

asked Feb 23, 2011 at 2:31

295 votes

21 answers

48k views

Really advanced techniques of integration (definite or indefinite)

integration soft-question definite-integrals indefinite-integrals big-list

user3002473

8,509

asked Sep 23, 2014 at 0:21

277 votes

4 answers

73k views

Norms Induced by Inner Products and the Parallelogram Law

linear-algebra functional-analysis normed-spaces inner-products

Hans Parshall

5,910

asked Feb 13, 2011 at 4:37

277 votes

3 answers

15k views

How does one prove the determinant inequality $\det\left(6(A^3+B^3+C^3)+I_{n}\right)\ge 5^n\det(A^2+B^2+C^2)$?

linear-algebra matrices inequality determinant hermitian-matrices

math110

1

asked Jul 8, 2014 at 16:41

275 votes

8 answers

62k views

Please explain the intuition behind the dual problem in optimization.

optimization convex-optimization intuition lagrange-multiplier karush-kuhn-tucker

littleO

48.5k

asked Oct 29, 2012 at 3:23

211 votes

22 answers

37k views

Is it faster to count to the infinite going one by one or two by two? [closed]

elementary-set-theory

Thomas Ayoub

1,615

asked Feb 3, 2014 at 10:13

202 votes

34 answers

40k views

List of interesting math videos / documentaries

soft-question big-list

user17762

asked Jan 25, 2011 at 3:02

193 votes

1 answer

7k views

Generalizing $\int_{0}^{1} \frac{\arctan\sqrt{x^{2} + 2}}{\sqrt{x^{2} + 2}} \, \frac{\operatorname dx}{x^{2}+1} = \frac{5\pi^{2}}{96}$

integration definite-integrals special-functions

Sangchul Lee

145k

asked Nov 25, 2013 at 12:51

187 votes

12 answers

322k views

Inverse of the sum of matrices

linear-algebra matrices inverse

Tomek Tarczynski

2,584

asked Jan 16, 2011 at 20:48

186 votes

8 answers

196k views

Proof that the trace of a matrix is the sum of its eigenvalues

linear-algebra matrices eigenvalues-eigenvectors trace

JohnK

5,750

asked Oct 30, 2013 at 22:11

183 votes

7 answers

284k views

Transpose of inverse vs inverse of transpose

matrices inverse transpose

Void Star

2,265

asked Mar 25, 2013 at 0:52

178 votes

12 answers

81k views

What is $dx$ in integration?

calculus infinitesimals

Sachin Kainth

6,343

asked Sep 21, 2012 at 17:35

168 votes

9 answers

15k views

Why do people use "it is easy to prove"?

soft-question math-history proof-writing

oleksii

865

asked Jul 29, 2011 at 10:43

167 votes

7 answers

90k views

Intuitively, what is the difference between Eigendecomposition and Singular Value Decomposition?

linear-algebra eigenvalues-eigenvectors svd diagonalization

user541686

12.7k

asked Mar 4, 2013 at 6:36

165 votes

8 answers

179k views

What is the difference between "singular value" and "eigenvalue"?

eigenvalues-eigenvectors definition spectral-theory svd singular-values

Ramon

1,659

asked Apr 3, 2012 at 3:19

159 votes

7 answers

32k views

Is Apple ipad / tablet good for mathematics students? [closed]

soft-question education

T. Webster

2,964

asked Sep 9, 2012 at 7:38

159 votes

20 answers

20k views

How to distinguish between walking on a sphere and walking on a torus?

geometry algebraic-topology soft-question surfaces big-list

Julien__

2,415

asked Jul 2, 2014 at 14:54

155 votes

6 answers

217k views

Is the product of two Gaussian random variables also a Gaussian?

probability probability-theory random-variables normal-distribution

jamaicanworm

3,964

asked Jan 21, 2012 at 18:46

151 votes

1 answer

12k views

Is the following matrix invertible?

linear-algebra matrices inverse

Yongkai

1,739

asked Jul 26, 2012 at 18:04

148 votes

2 answers

43k views

Examples of bijective map from $\mathbb{R}^3\rightarrow \mathbb{R}$

real-analysis elementary-set-theory examples-counterexamples

Marso

31.5k

asked Aug 16, 2012 at 20:01

142 votes

1 answer

5k views

Identification of a curious function

calculus sequences-and-series functions special-functions game-theory

Yuval Filmus

55.7k

asked Aug 18, 2013 at 7:44

133 votes

15 answers

79k views

Why is $1$ not a prime number?

abstract-algebra elementary-number-theory ring-theory prime-numbers terminology

bryn

8,641

asked Jul 20, 2010 at 21:08

131 votes

10 answers

6k views

what is expected from a PhD student?

soft-question advice

Tomas Jorovic

3,783

asked Aug 5, 2013 at 17:11

129 votes

20 answers

88k views

Real life applications of Topology

general-topology soft-question big-list applications

Bhargav

2,879

asked Oct 18, 2011 at 16:36

118 votes

2 answers

82k views

Prove that simultaneously diagonalizable matrices commute

linear-algebra matrices

diimension

3,210

asked Nov 13, 2012 at 4:54

117 votes

10 answers

12k views

Find the average of $\sin^{100} (x)$ in 5 minutes?

integration approximation

Please Delete Account

asked Mar 2, 2011 at 2:20

Stack Exchange Network

current community

your communities

more stack exchange communities

448 Bookmarks

Is $\frac{\textrm{d}y}{\textrm{d}x}$ not a ratio?

A proof for $\dim(R[T])=\dim(R)+1$ without prime ideals?

Does $\pi$ contain all possible number combinations?

'Obvious' theorems that are actually false

What is the importance of eigenvalues/eigenvectors?

Really advanced techniques of integration (definite or indefinite)

Norms Induced by Inner Products and the Parallelogram Law

How does one prove the determinant inequality $\det\left(6(A^3+B^3+C^3)+I_{n}\right)\ge 5^n\det(A^2+B^2+C^2)$?

Please explain the intuition behind the dual problem in optimization.

Is it faster to count to the infinite going one by one or two by two? [closed]

List of interesting math videos / documentaries

Generalizing $\int_{0}^{1} \frac{\arctan\sqrt{x^{2} + 2}}{\sqrt{x^{2} + 2}} \, \frac{\operatorname dx}{x^{2}+1} = \frac{5\pi^{2}}{96}$

Inverse of the sum of matrices

Proof that the trace of a matrix is the sum of its eigenvalues

Transpose of inverse vs inverse of transpose

What is $dx$ in integration?

Why do people use "it is easy to prove"?

Intuitively, what is the difference between Eigendecomposition and Singular Value Decomposition?

What is the difference between "singular value" and "eigenvalue"?

Is Apple ipad / tablet good for mathematics students? [closed]

How to distinguish between walking on a sphere and walking on a torus?

Is the product of two Gaussian random variables also a Gaussian?

Is the following matrix invertible?

Examples of bijective map from $\mathbb{R}^3\rightarrow \mathbb{R}$

Identification of a curious function

Why is $1$ not a prime number?

what is expected from a PhD student?

Real life applications of Topology

Prove that simultaneously diagonalizable matrices commute

Find the average of $\sin^{100} (x)$ in 5 minutes?