Mathematics
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Stephan Kulla
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172 Answers

Votes Activity Newest
24
What are some things we can prove they must exist, but have no idea what they are?
Sep 26 '15 at 23:20
24
Find the eigenvalues of a projection operator
Feb 20 '15 at 14:36
16
Can a function be differentiable at the end points of its (closed interval) domain?
May 23 '15 at 10:23
10
Why it is absolutely mistaken to cancel out differentials?
May 8 '15 at 15:56
9
Most general $A \subseteq \mathbb R$ to define derivative of $f: A \to \mathbb R$?
Jun 23 '12 at 22:04
8
Formula for the sequence repeating twice each power of $2$
Jun 24 '12 at 18:04
7
Innocent looking open problems in real analysis
Feb 9 '15 at 15:50
6
Can any Real number be typed in a computer?
Nov 8 '15 at 19:18
6
Are there mathematical objects that have been proved to exist but cannot be described in words?
May 16 '15 at 16:51
5
Does $f$ measurable $\iff$ $|f|$ measurable?
Nov 9 '15 at 17:39
5
Vector Space spanned by the polynomials $p_n(x) = x^n$
Jul 15 '15 at 9:44
5
Evaluate $\lim_{x \to 0} \frac{\sin(x³)}{x}$ without L'hopital rule
May 18 '15 at 13:13
4
Difference between {… | …} and {… : …}
Sep 21 '15 at 10:32
4
Limit and limit points
Jul 23 '15 at 14:58
4
Does group inverse commute with multiplication for all groups?
Jul 21 '15 at 12:16
4
Any (n-1) vectors from system X are linearly independent $\nRightarrow$ X is linearly independent
May 13 '15 at 7:53
4
the elements of Cantor's discontinuum
May 12 '15 at 23:00
4
Necessity of the Completeness Axiom in Calculus
Apr 20 '15 at 14:50
4
A sequence in which liminf < limsup
Feb 23 '15 at 17:31
4
Convergence of $\sum_{n=1}^{\infty}\left(\, \frac{1}{n} - \frac{1}{n + 2}\,\right)$
Dec 11 '14 at 18:43
4
Is there an epsilon-delta definition of the second derivative?
Jun 24 '12 at 10:48
4
Lie algebra of R^n
Apr 20 '14 at 19:53
3
How to solve $\sum_{k=1}^n\frac{k}{n^2+k}$?
Aug 30 '15 at 20:47
3
What is the implication that $\| \cdot \|_2$ and $\| \cdot \|_\infty$ are equivalent norms on $\mathbb{R^2}$
Aug 4 '15 at 8:13
3
Which is the domain set?
Aug 2 '15 at 17:40
3
Question about a real sequence
Jul 14 '15 at 15:44
3
How to determine whether a set is a vector space or not?
May 24 '15 at 13:02
3
Polynomial Functional Equation: $f(x)f(y)+2=f(x)+f(y)+f(xy)$
May 19 '15 at 18:47
3
Prove $f(x) =x^2$ is continuous at $x_0=2$ using the $\epsilon$-$\delta$ definition
May 14 '15 at 22:34
3
How do I describe a set of names?
Jan 30 '15 at 16:50
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