User crf - Mathematics Stack Exchange

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5

17

votes

8

answers

656

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What is it about modern set theory that prevents us from defining the set of all sets which are not members of themselves?

set-theory

aug 17 at 20:48 Hurkyl 21.5k

2

votes

2

answers

560

views

Prove that $f(x)=x$ is Riemann-integrable on $[0,1]$ with $\int_0^1xdx=\frac{1}{2}$

jan 11 at 7:24 proximal 2,229

1

4

votes

4

answers

500

views

Let X and Y be random variables with joint pdf $f(x,y)=x+y$ for $0<x<1$ and $0<y<1$. Are X and Y independent? My heart says yes but my math says no.

homework probability

aug 12 at 3:38 Ikuyasu 12

1

vote

1

answer

445

views

Proof involving a convex set

homework convex-analysis economics

nov 12 '11 at 4:03 Srivatsan 15.7k

3

votes

1

answer

393

views

Two related questions about flipping a coin an infinite number of times

probability-theory

apr 16 '12 at 2:28 Jim Belk 13.7k

1

vote

1

answer

384

views

Show that $\det(A-\lambda I)=\det(B-\lambda I)$

homework linear-algebra

oct 5 '11 at 12:28 Michael Hardy 48.4k

1

10

votes

9

answers

272

views

Why is it legit to evaluate $\lim_{x\rightarrow 1} \frac{(x-1)(x+1)}{x-1}$ by cancelling common factors?

limit

feb 6 at 22:51 MiauPiau 6

0

votes

2

answers

260

views

Finding the matrix associated with a linear transformation

homework linear-algebra matrices vector-spaces

apr 1 at 17:02 somaye 2,116

1

vote

1

answer

259

views

Why does the “auxiliary problem” method work to find a feasible dictionary?

optimization linear-programming

may 23 '12 at 10:58 Will Orrick 2,532

2

votes

1

answer

236

views

Prove that if $f$ is Riemann-Integrable on $ [0,1]$ then $\lim_{c\rightarrow 0} \int_c^1 f(x)dx$ exists and is equal to $\int_0^1 f(x)dx$

homework real-analysis integral limit improper-integrals

jan 28 at 9:58 Thomas 1,223

2

votes

2

answers

202

views

Baby Rudin problem 3.22: prove Baire's theorem. Am I going in a reasonable direction?

homework real-analysis general-topology baire-category

dec 25 at 22:04 BenjaLim 16.8k

1

6

votes

3

answers

193

views

Help understanding $e^{it}=\cos t+i\sin t$ by way of matrices and vector fields

matrices differential-equations complex-numbers

sep 5 at 7:04 crf 1,116

3

votes

2

answers

192

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Interesting or non-obvious finite subsets of the natural numbers

elementary-number-theory soft-question natural-numbers

sep 12 at 10:56 Sean Eberhard 2,708

2

3

votes

3

answers

184

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Is there a quicker, nicer way to show that the union of compact sets is not necessarily compact?

homework real-analysis general-topology

mar 1 at 15:50 TonyK 11.9k

2

votes

3

answers

173

views

Is the set of all $n\times n$ matrices, such that for a fixed matrix B AB=BA, a subspace of the vector space of all $n\times n$ matrices?

homework linear-algebra vector-spaces

oct 20 '11 at 18:58 Jack Schmidt 20.5k

2

votes

1

answer

171

views

Proving Hölder's Inequality

homework real-analysis integral inequality

jan 25 at 7:05 Paul 8,672

2

5

votes

3

answers

157

views

Is a broken clock right twice a day?

periodic-functions

mar 31 at 8:21 Christian Blatter 32.7k

2

votes

1

answer

147

views

Find the probability that the second customer to arrive has to wait to be served if arrival time is exponential and serving time is uniform

homework probability probability-distributions queueing-theory

aug 13 at 8:43 Did 103k

1

vote

1

answer

145

views

Proving Schwarz inequality for complex numbers using calculus

homework real-analysis inequality multivariable-calculus

sep 28 at 11:45 Martin Argerami 16.9k

4

5

votes

2

answers

130

views

When does the next bus come?

probability queueing-theory

mar 28 at 5:01 Joe Turner 353

1

5

votes

2

answers

120

views

Calculate $\left\Vert \begin{bmatrix}1 & 2\\ 2 & 4 \end{bmatrix} \right\Vert$

linear-algebra matrices norm

jan 8 at 7:19 user17762 76.6k

1

vote

2

answers

120

views

Why do these two methods of calculating the probability of winning a best-of-7 series give the same answer?

probability

jul 18 at 19:26 Arkamis 7,977

1

3

votes

1

answer

106

views

Show that the Riemann-Stieltjes integral exists

homework real-analysis integral

jan 16 at 8:44 lyj 1,416

2

votes

1

answer

102

views

Is the “field” I learned about in analysis different from the “field” I learned about in econometrics?

probability-theory field-theory

sep 7 at 0:42 Qiaochu Yuan 118k

5

votes

2

answers

101

views

Why does it always take n numbers to characterize a point in n-dimensional space (or does it)?

coordinate-systems polar-coordinates

jun 8 '12 at 20:12 Qiaochu Yuan 118k

2

votes

3

answers

98

views

Problem relating convex sets and optimization

homework convex-analysis economics

dec 24 '11 at 16:30 Byron Schmuland 15.4k

2

votes

1

answer

97

views

How to prove that there exist a concave function and $\gamma\in[0,1]$ and some other numbers which satisfy an inequality

inequality economics utility

sep 17 at 9:22 ivan 878

2

votes

2

answers

96

views

From which areas of mathematics does consumer theory in microeconomics spawn?

economics

aug 31 at 23:13 Michael Greinecker♦ 12.5k

3

votes

2

answers

94

views

Probability that judges are right about their verdict

homework probability

apr 15 '12 at 19:17 André Nicolas 162k

2

votes

2

answers

93

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Help understanding Rudin's proof of the chain rule

calculus real-analysis limit derivatives

dec 2 at 10:43 wj32 2,234

crf

59 Questions