User yiyi - Mathematics Stack Exchange

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	1,978 reputation	bio	website		visits	member for	1 year, 4 months
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9

20

votes

2

answers

553

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a problem from 1977 all Soviet Union Mathematical Olympiad

combinatorics

nov 27 at 9:08 Marc van Leeuwen 23.9k

3

12

votes

2

answers

244

views

Does every closed curve contain the vertices of a square?

geometry soft-question

jan 19 at 13:10 K.HARISH 1

8

votes

2

answers

75

views

$\sum \limits_{k=1}^{\infty} \frac{6^k}{\left(3^{k+1}-2^{k+1}\right)\left(3^k-2^k\right)} $ as a rational number.

calculus sequences-and-series

mar 3 at 12:48 Arjang 2,447

1

8

votes

1

answer

306

views

Confused about an integral from MIT integration bee 2012

calculus

dec 15 at 17:08 Nameless 7,952

8

votes

2

answers

190

views

Wrong solution for $\int \frac{1 - e^x}{e^x}\, dx$

homework calculus

mar 31 '12 at 18:26 Michael Hardy 48.2k

7

votes

1

answer

109

views

$\int 5\sqrt{x^3+2x}\, \textrm{d}x$

calculus

dec 11 at 16:53 George 46

6

votes

2

answers

90

views

Find the derivative in term of $x$ and $y$.

calculus

apr 20 at 1:05 André Nicolas 161k

4

6

votes

1

answer

129

views

“coffin” or killer problem - Oral entrance exams to the math department of Moscow State University

geometry

jan 20 at 9:03 Mohan 2,724

6

votes

1

answer

225

views

is there a cardinality between the rational and the irrationals?

reference-request cardinals

sep 17 at 7:57 Asaf Karagila 91.4k

1

6

votes

1

answer

302

views

What do these arrows mean? (Froda's Thm)

notation definition

may 12 '12 at 20:37 Zev Chonoles 54k

5

votes

2

answers

89

views

Question regarding usage of absolute value within natural log in solution of differential equation

homework differential-equations absolute-value

feb 23 at 2:09 Iuli 3,091

5

votes

1

answer

149

views

Checking to make sure I understand the English in this math problem.

calculus

dec 19 at 15:24 yiyi 1,978

1

5

votes

3

answers

204

views

How to take the derivative of $x!$

calculus limit derivatives

dec 5 at 8:05 marty cohen 6,869

5

votes

0

answers

105

views

Help make Wonder Woman's box big.

calculus

nov 7 at 13:17 Per Manne 4,429

2

5

votes

3

answers

551

views

The most common theorems taught in Abstract Algebra

abstract-algebra soft-question self-learning

feb 3 '12 at 16:22 Arturo Magidin 158k

4

votes

1

answer

42

views

Is the answer sheet wrong?

calculus

mar 25 at 0:43 Thomas 10.8k

4

votes

2

answers

96

views

Why does the answer sheet solve this problem with d/dt?

calculus

mar 24 at 15:30 Community♦ 1

1

4

votes

1

answer

354

views

half-derivative of $x^2$

reference-request fractional-calculus

feb 27 at 20:02 Mhenni Benghorbal 14.2k

4

votes

0

answers

131

views

Problem with fractional exponents

homework algebra-precalculus

aug 29 at 10:46 yiyi 1,978

4

votes

1

answer

130

views

Need help solving Recursive series

homework calculus sequences-and-series

apr 23 '12 at 7:32 ziyuang 749

1

4

votes

1

answer

175

views

KY Birds…which book is that from.

reference-request soft-question

jan 28 '12 at 19:45 user7610 86

2

3

votes

2

answers

50

views

Geometric solution to classic committee problem

combinatorics geometry finite-fields combinatorial-geometry combinatorial-designs

may 13 at 3:19 zyx 11.1k

1

3

votes

2

answers

79

views

Is the solution guide wrong?

calculus

may 1 at 12:39 Tharsis 875

3

votes

1

answer

49

views

Whether $\sum \limits_{n=1}^{\infty} \dfrac{\left(-1\right)^n n^2}{n^2+5} =\sum \limits_{n=1}^{\infty} \left(-1\right)^n -\dfrac{5}{n^2+5} $

calculus sequences-and-series

mar 8 at 6:04 Community♦ 1

3

votes

2

answers

66

views

Does “indeterminate” mean “divergent”?

calculus sequences-and-series terminology

mar 8 at 5:58 Community♦ 1

3

votes

1

answer

68

views

Alternative method for solving this equation involving a series?

calculus sequences-and-series

mar 3 at 17:18 vonbrand 6,618

3

votes

1

answer

110

views

(Paul Bartha and Christopher Hitchcock, “The Shooting Room Paradox and Conditionalizing on Measurably Challenged Sets,” Synthese, March 1999)

probability

jan 20 at 7:58 David Moews 10.2k

1

3

votes

3

answers

185

views

Confused about the answer of AP BC 2010 # 3a

calculus

dec 26 at 14:41 Elias 3,003

3

votes

2

answers

194

views

are there other integrals like Gabriel's Horn?

calculus soft-question

dec 11 at 3:31 Jason DeVito 14.3k

3

votes

3

answers

89

views

$F(x)=\int_1^{3x} \frac{1}{t}\, \mathrm{d}t$ Find $F^{\prime}(x)$

calculus

nov 21 at 11:55 Amihai Zivan 1,083

yiyi

155 Questions