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abnry
  • Member for 11 years, 9 months
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41 votes

When to give up on a hard math problem?

31 votes
Accepted

Fractional Calculus: Motivation and Foundations.

24 votes
Accepted

integral of $x^2e^{-x^2}~dx$ from $-\infty$ to $+\infty$

20 votes
Accepted

What's the best way to measure mathematical ability?

19 votes

Solutions for x!/y!=(y+1)!

19 votes
Accepted

Prove that if $3\mid a^2+b^2$ then $3\mid a$ and $3\mid b$.

18 votes
Accepted

If $\sum a_n$ converges, prove $\sum a_n^3$ converges

15 votes

Accidents of small $n$

15 votes
Accepted

Is indefinite integration largely a heuristic or it can be mechanical too?

13 votes
Accepted

$\operatorname{tr}(A)=\operatorname{tr}(A^{2})= \ldots = \operatorname{tr}(A^{n})=0$ implies $A$ is nilpotent

13 votes

Prove $\int\cos^n x \ dx = \frac{1}n \cos^{n-1}x \sin x + \frac{n-1}{n}\int\cos^{n-2} x \ dx$

12 votes

How to prove $\int_{-\infty}^{+\infty} f(x)dx = \int_{-\infty}^{+\infty} f\left(x - \frac{1}{x}\right)dx?$

12 votes

Are there 3 trig functions or are there 6 trig functions?

12 votes
Accepted

Equation of a 3D spiral

11 votes

Good math bed-time stories for children?

11 votes
Accepted

Are there $a,b \in \mathbb{N}$ that ${(\sum_{k=1}^n k)}^a = \sum_{k=1}^n k^b $ beside $2,3$

11 votes

Prove that $\sin(2^n \alpha)$ can be arbitrarily small

10 votes

Is high school contest math useful after high school?

9 votes
Accepted

Question on closed sets

9 votes

Why do some series converge and others diverge?

8 votes

Functional inequation on $\mathbb{R}$: $f\left(x+y^2\right)-f(x)\geq y$

8 votes

Prove that if $n$ is not divisible by $5$, then $n^4 \equiv 1 \pmod{5}$

8 votes
Accepted

Functions for which $\int f(g(x))\, \mathrm dx = f\left(\int g(x) \, dx\right)$

8 votes
Accepted

The inverse of a perturbed identity matrix.

8 votes

What are all finite groups such that all isomorphic subgroups are identical?

8 votes
Accepted

Why is $\lim_{n\rightarrow\infty}\int f_n \mathrm{d} \mu=\int f \mathrm{d} \mu$ not true

8 votes
Accepted

for each $\epsilon >0$ there is a $\delta >0$ such that whenever $m(A)<\delta$, $\int_A f(x)dx <\epsilon$

8 votes
Accepted

Any finite set is compact; what exactly is a finite set?

7 votes

Problems with limit of factorials: $\;\lim_{n\to\infty}\frac{1!+2!+\ldots+n!}{n!}\;$

7 votes

$\sum a_n$ converges $\implies\ \sum a_n^2$ converges?

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