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Sebastian Schulz
  • Member for 5 years, 4 months
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31 votes

Calculate area of Ellipse without calculus?

6 votes

Example of sequence such that $x_n $ converges to zero but $(x_n)^\frac{1}{n}$ diverges?

4 votes

For m,n integers, prove (or disprove) that if $n(n-1) | (m-1)(m+1)$ then

3 votes
Accepted

Proving $\phi(G)$ is Abelian if $\phi$: $G \to H$ is a group homomorphism

3 votes
Accepted

Laurent series of $\frac1{1-z}$

3 votes
Accepted

Inner Product on Lie Algebra So the Exponential Map Becomes the Matrix Exponential?

2 votes

How to get the two-digit number which is 3/8 of the number I get by swapping the digits of the original?

2 votes
Accepted

How to find the values of $k$ if $2k \in \mathbb{Z}$ and $\frac{2}{k}\in \mathbb{Z}$

2 votes

if $\lim (a_nb_n) = \infty$ and $0<b_n<a_n$ for almost every $n$, then $\lim a_n =\infty$

2 votes
Accepted

Does the mapping $\left \langle v,w \right \rangle= \text{max}(v_i \cdot w_i)$ define a scalar product?

2 votes
Accepted

Is there $a,b \in \mathbb C^2$ $b\neq 0$ such that if $t \in \mathbb C, |t|<1$, then $|a+tb|=1$?

2 votes
Accepted

Does There exist a Continuous Surjection from $S^1$ to $[0, 1]$?

2 votes
Accepted

Sorting 10 pairs of socks into 4 drawers

1 vote

A weird linear algebra exam question

1 vote

Does Part of Line Cut Through Square

1 vote

Limit of a series

1 vote
Accepted

equivalence of Euclidean and manhattan metric

1 vote

Central extension and direct product

1 vote

Intersection of unit sphere and ellipsoid

1 vote

$f_*$ isomorphism $\Rightarrow$ $f$ isomorphism?

1 vote

Simplify ((A ∪ B) ∩ C) ∪ ((C − A) − B).

1 vote
Accepted

If $\sin(x)+\sin(y)\ge \cos(\alpha) \times \cos(x)$ $\forall x\in \mathbb R$, then $\sin(y)+\cos(\alpha)$ is equal to?

1 vote

The transformation group of all bijections has a subset V of all strictly increasing bijections, show its a subgroup.

1 vote

How many consecutive zeros to the left of the decimal does $125^{14} \times48^{8}$ have?

1 vote
Accepted

Determine $s: M_{2x2}(\mathbb{R}) \rightarrow\ \mathbb{R}^{3}$ such us $ST=Id$ given $T:\mathbb{R}^{3}\rightarrow\ M_{2x2}(\mathbb{R})$ injective

0 votes

Condition on $u$ so that $ |\frac{x \cdot u } {u \cdot u}u - x |< |x|$

0 votes

Proof involving homomorphism between $\Bbb Z^n$ and an abelian group G

0 votes

Showing that ~ is an equivalence relation

0 votes

Finding a function with some requirements

0 votes

$(x,y,z)\in \mathbb{R}^3 \mapsto f(x,y,z):= (x^2+y^2+z^2+8)^2-36(x^2+y^2)$. Let $M:=f^{-1}(0)$. Find the $T_cM$ and provide a basis for it.