User AlanH - Mathematics Stack Exchange

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	location	Antarctica
	age	77
visits	member for	7 months
	seen	6 hours ago
stats	profile views	148

	792 reputation	bio	website	math.stackexchange.com/users/…	visits	member for	7 months
219 badges		location	Antarctica		seen	6 hours ago

173

230

votes

16

answers

41

kviews

What are imaginary numbers?

definition

nov 6 at 22:22 KeithS 1,051

103

206

votes

33

answers

17

kviews

Do complex numbers really exist?

may 5 at 4:54 l19 115

108

179

votes

8

answers

15

kviews

Is $dy/dx$ not a ratio?

calculus

mar 14 at 3:35 isomorphismes 845

183

163

votes

23

answers

10

kviews

Proofs that every mathematician should know?

soft-question big-list

mar 25 at 0:36 Glen O 3,177

54

151

votes

13

answers

17

kviews

Unusual 5th grade problem, how to solve it

elementary-number-theory diophantine-equations

may 1 at 13:18 doraemonpaul 3,026

19

120

votes

4

answers

4

kviews

Can you answer my son's fourth-grade homework question: Which numbers are prime, have digits adding to ten and have a three in the tens place?

elementary-number-theory recreational-mathematics analytic-number-theory

may 8 at 4:56 Dale M 404

31

56

votes

5

answers

3

kviews

What is the Riemann-Zeta function?

terminology complex-analysis prime-numbers riemann-zeta

jan 2 '12 at 14:46 joriki 92.7k

8

53

votes

10

answers

4

kviews

100 Soldiers riddle

combinatorics pigeonhole-principle puzzle inclusion-exclusion

feb 1 '12 at 19:06 miracle173 840

34

46

votes

17

answers

4

kviews

Striking applications of integration by parts

calculus big-list

may 3 at 13:19 DepeHb 494

12

44

votes

3

answers

2

kviews

Cute Determinant Question

linear-algebra determinant

jul 30 at 9:55 J. M. 38.9k

26

39

votes

4

answers

1

kviews

Showing that $\int\limits_{-a}^a \frac{f(x)}{1+e^{x}} \mathrm dx = \int\limits_0^a f(x) \mathrm dx$, when $f$ is even

homework calculus real-analysis integration

oct 21 at 3:06 user17762 76.4k

15

35

votes

5

answers

2

kviews

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

approximation

oct 8 '11 at 14:53 Michael Hardy 48.2k

33

32

votes

4

answers

3

kviews

Lesser-known integration tricks

calculus big-list integration

mar 25 '12 at 16:59 Linda Collins Sandgren 41

11

32

votes

7

answers

1

kviews

Inequality: $(a^3+a+1)(b^3+b+1)(c^3+c+1) \leq 27$

inequality

apr 1 at 20:01 Iuli 3,093

14

31

votes

5

answers

900

views

How to prove this identity $\pi=\sum\limits_{k=-\infty}^{\infty}\left(\frac{\sin(k)}{k}\right)^{2}\;$?

sequences-and-series trigonometry pi

may 7 at 15:34 robjohn♦ 59.9k

8

24

votes

3

answers

1

kviews

Asymptotic (divergent) series

real-analysis sequences-and-series reference-request divergent-series

jun 13 '12 at 20:20 Américo Tavares 20.7k

7

21

votes

5

answers

1

kviews

How do you calculate the decimal expansion of an irrational number?

numerical-methods approximation irrational-numbers pi

aug 15 at 15:54 Argon 9,263

6

20

votes

9

answers

3

kviews

Prove $2^{1/3}$ is irrational.

elementary-number-theory irrational-numbers

aug 18 at 16:47 Community♦ 1

5

19

votes

11

answers

811

views

Comparing $\sqrt{1001}+\sqrt{999}\ , \ 2\sqrt{1000}$

algebra-precalculus problem-solving

6h ago Mikael Jensen 26

10

17

votes

3

answers

360

views

How much time is too much (to put into a single problem)?

soft-question advice

mar 29 at 18:43 Feanor 2,867

6

16

votes

3

answers

323

views

Finding all integer solutions of $5^x+7^y=2^z$

number-theory elementary-number-theory diophantine-equations contest-math

apr 3 at 7:31 Ivan Loh 7,573

9

15

votes

2

answers

240

views

How to find the value of $\sin{\dfrac{\pi}{14}}+6\sin^2{\dfrac{\pi}{14}}-8\sin^4{\dfrac{\pi}{14}}$

trigonometry

apr 18 at 13:59 TMM 7,156

7

15

votes

1

answer

1

kviews

Is the following matrix invertible?

linear-algebra matrices

jul 27 at 1:46 torrho 93

13

14

votes

5

answers

1

kviews

Math GRE Subject Exam

education advice

mar 31 at 6:19 yiyi 1,978

10

14

votes

5

answers

501

views

Evaluate: $\int_0^{\pi} \ln \left( \sin \theta \right) d\theta$

complex-analysis integral logarithms

may 5 at 22:04 Ma Ming 2,045

3

13

votes

3

answers

396

views

Solving a difficult recursion via generating functions

homework recurrence-relations power-series generating-functions

may 1 at 1:17 vonbrand 6,618

4

12

votes

3

answers

565

views

If $\sum_{1}^{\infty}(a_n)^3$ diverges, does $\sum_{1}^{\infty}(a_n)$?

homework sequences-and-series divergent-series

jan 5 '12 at 16:04 GEdgar 19k

3

11

votes

3

answers

296

views

Calculate:$y'$ for $y = x^{x^{x^{x^{x^{.^{.^{.^{\infty}}}}}}}}$ and $y = \sqrt{x+\sqrt{x+\sqrt{x+\sqrt{x+…\infty}}}}$

calculus derivatives

mar 21 at 16:10 kalpeshmpopat 947

5

11

votes

6

answers

1

kviews

Why are generating functions useful?

combinatorics generating-functions

jun 9 '12 at 13:47 Dylan Moreland 13.4k

2

11

votes

4

answers

376

views

Integrate $\sin^3x/(\sin^3x + \cos^3x)$?

integration

oct 28 at 14:52 minthao_2011 560

AlanH

84 Favorites