Skip to main content
Leitingok's user avatar
Leitingok's user avatar
Leitingok's user avatar
Leitingok
  • Member for 12 years, 11 months
  • Last seen more than 5 years ago
41 votes
2 answers
2k views

A question on Taylor Series and polynomial

19 votes
3 answers
8k views

Show that $A_n=\sum\limits_{k=1}^n \sin k $ is bounded?

19 votes
3 answers
6k views

Show that $f(x+y)=f(x)+f(y)$ implies $f$ continuous $\Leftrightarrow$ $f$ measurable [duplicate]

18 votes
5 answers
5k views

Question about Riemann integral and total variation

15 votes
2 answers
1k views

Why this set is dense in $C_0(\mathbb{R})$?

14 votes
2 answers
499 views

If $a,b,c$ are positive integers,and $\cfrac{a}{b}+\cfrac{b}{c}+\cfrac{c}{a}$ and $\cfrac{b}{a}+\cfrac{c}{b}+\cfrac{a}{c}$ are integers then $a=b=c$

12 votes
2 answers
268 views

Showing a set is countable or not.

12 votes
0 answers
256 views

Showing a series is convergent. [duplicate]

10 votes
2 answers
3k views

Maximum of sum of finite modulus of analytic function.

10 votes
3 answers
291 views

Question about members in sets

9 votes
2 answers
433 views

A question about linear subspace and subfield

9 votes
3 answers
5k views

Showing $\sup \{ \sin n \mid n\in \mathbb N \} =1$ [closed]

8 votes
2 answers
388 views

Measurable functions with the same integral over a set

8 votes
3 answers
430 views

Showing convergence of a series

7 votes
1 answer
2k views

Showing $\mathbb{Q}$ is homeomorphic to $\mathbb{Q}^2$

7 votes
2 answers
152 views

A question about convex open set in a topological vector space.

7 votes
1 answer
3k views

An operator has closed range if and only if the image of some closed subspace of finite codimension is closed.

7 votes
2 answers
2k views

Is an increasing, bounded and continuous function on $[a,+\infty)$ uniformly continuous?

6 votes
2 answers
207 views

A question about measure on $\mathbb{R}^2$

6 votes
3 answers
7k views

How to compute $ \int_0^1 {e^{-x^2}} dx$

6 votes
1 answer
224 views

Showing a sequence convergence

5 votes
7 answers
324 views

Prove that $\int_0^{+\infty} \frac{\ln x}{a^2+x^2} dx = \frac{\pi\ln a}{2a}$

5 votes
1 answer
470 views

Application for mean value theorem

5 votes
2 answers
1k views

Is convex open set in $\mathbb{R}^n$ is regular?

5 votes
2 answers
753 views

Showing range is countable

5 votes
2 answers
226 views

How many fields inside $\mathbb R$?

5 votes
1 answer
592 views

If $f=F'$ and $|f|$ is Riemann integrable, how to show that $f$ is Riemann integrable?

5 votes
2 answers
588 views

Showing the derivative of this function is equal to $0$

5 votes
1 answer
99 views

Showing the limit is $+\infty$

4 votes
2 answers
127 views

Showing whether two numbers are equal or not