2,668 reputation
2336
bio website ephorie.de
location Germany
age 44
visits member for 4 years, 4 months
seen 13 hours ago

just an amateur fascinated by math


Jun
9
comment Question about direct sum of function space
I think what confuses me is that we start with $\mathbb R^3$ and end up with it. It would come more natural if we started with $\mathbb R$ and after taking the direct sum three times would end in $\mathbb R^3$.
Jun
9
comment Question about direct sum of function space
@Dactyl: Could you please elaborate? So I don't get it...
Jun
9
asked Question about direct sum of function space
Jun
9
comment Function for concatenated semicircles
WA-plot: wolframalpha.com/input/?i=Plot+%28-1%29^%28Floor%5B%28x%2F2+%2B+0.5%2‌​9%5D%29+Sqrt%5B1+-+%28x+-+2+Floor%5Bx%2F2+%2B+0.5%5D%29^2%5D - How did you find it?
Jun
9
comment Function for concatenated semicircles
I now remember that I stumbled upon this phenomenon when you iterate trig funcs: wolframalpha.com/input/… - perhaps this helps and can be combined with some of the other ideas here?!?
Jun
9
comment Function for concatenated semicircles
@Zev: I don't know how to fix this, but I think it goes into the right direction. Floor func is ok.
Jun
9
comment Function for concatenated semicircles
@jspecter: No, please no piecewise def. @Theo: Infinite sums are ok, I think even necessary for the nearly perpendicular inflection points (=infinite slope).
Jun
9
asked Function for concatenated semicircles
Jun
5
comment Binomial model of stock price
I suggest the question being transferred here: quant.stackexchange.com
May
31
comment Throwing All Numbers From 2 to 12 With Two Dice
@crasic: You could reformulate it: On average, how many times must two 6-sided dice be rolled until all numbers from 2 to 12 appear at least once?
May
31
comment Throwing All Numbers From 2 to 12 With Two Dice
This sounds interesting. With one die its easy, see e.g. here: madandmoonly.com/doctormatt/mathematics/dice1.pdf p.9
May
31
comment Why is integration so much harder than differentiation?
Just for the record: Penrose discusses these matters on p. 103-120. Yet he gives no good reason why this is so (esp. for the symbolic case).
May
16
accepted integral transforms: why do roots in frequency domain correspond to eigenvalues in time domain (and how does it help solve differential equations)?
May
15
comment What is the importance of eigenvalues/eigenvectors?
+1: This is the clearest explanation I have seen so far about the connection between systems of differential equations and eigenvectors - impressive!
May
15
asked integral transforms: why do roots in frequency domain correspond to eigenvalues in time domain (and how does it help solve differential equations)?
May
13
awarded  Cleanup
May
13
revised Zeno-like riddle with additional complication: Runner with dog running back and forth at different speeds
deleted 23 characters in body
May
13
revised Zeno-like riddle with additional complication: Runner with dog running back and forth at different speeds
rolled back to a previous revision
May
13
accepted Zeno-like riddle with additional complication: Runner with dog running back and forth at different speeds
May
13
comment Zeno-like riddle with additional complication: Runner with dog running back and forth at different speeds
Ah, now I understand - Thank you!