123,719 reputation
8117240
bio website von-eitzen.de/math/tntrep.xml
location Bonn, Germany
age 49
visits member for 2 years, 3 months
seen 5 hours ago

I did study math and had a knack for it, but I am sooo out of that business now ...


Feb
7
reviewed Close Applications of infinity in real life
Feb
7
reviewed Close The domain of a function
Feb
7
answered Efficient algorithm for finding intervals in a DAG
Feb
7
comment The domain of a function
@labbhattacharjee With values like $3$ and $3.2$ occuring, the approximation $\pi\approx 3.1$ may be more practical to see what values of $n$ are possible.
Feb
7
reviewed Approve $f(x)=\cos(ax+b)$ find $f'(x)$ , $f''(x)$, $f'''(x)$, $f''''(x)$ and give a general form for $f^{(n)}( x)$ where there s cosinus
Feb
7
answered Flip the bulbs in minimum number of moves
Feb
7
comment Flip the bulbs in minimum number of moves
possible duplicate of board game: 10 by 10 light bulbs, minimum switches to get all off?
Feb
7
awarded  Enlightened
Feb
7
awarded  Nice Answer
Feb
6
revised La fonction $f$ admet-elle une fonction réciproque?
added 23 characters in body; edited title
Feb
6
comment La fonction $f$ admet-elle une fonction réciproque?
"Hello, I have a little problem with an exercise. Consider the function $f\colon[-1,1]\to [-\tfrac12,\tfrac12]$ defined by $f(x)=\frac x{1+x^2}$. Show that $f$ admits an inverse function and define that function. Thanks for your help" (I guess, je suis desole that I don't speak a siungle word of French)
Feb
6
comment Change or cancel flight?
@AbhimanyuArora depends on where you set the base. If the 135\$ in case of no-show are considered a loss, the base point is before originally booking the flight and then you do indeed loose 200\$ fee in the second option. - As it turns out the best option would be neither no show (135 loss) nor refund (200 loss) but to actually fly (enjoy the flight in exchange for 135\$)
Feb
6
answered Change or cancel flight?
Feb
6
answered angle in triangle of pre-known measure
Feb
6
answered How to prove a series is greater than zero over an interval?
Feb
6
answered Evaluating a limit.
Feb
6
answered False proof of convergent harmonic series
Feb
6
answered Find a non-diagonizable matrix that commutes with $\begin{bmatrix}0 & 0& -1\\1 & 1 &1\\0 & 0 & 1\end{bmatrix}$
Feb
6
comment Bilinear form dimension
I assume you mean the space of bilinear forms, i.e. maps $V\times W\to k$ that are linear in both $V$ and $W$. Then note that this space is essentially the space of linear maps $V\to W^*$ where $W^*$ is the dual space of $W$.
Feb
6
revised Bilinear form dimension
added 1 characters in body