1,566 reputation
825
bio website fuz.su/~fuz
location Berlin, Germany
age 19
visits member for 3 years, 9 months
seen yesterday

I am a student of computer science and mathematics at the Humboldt University of Berlin.


Sep
21
comment Easy proof, that $\rm e\notin \mathbb Q$
@Yuval That is actually how we did this. The problem is, that the students in my class don't like proofs containing too many “It is easy to see that...”s. The proof using this strategie filled one A4 page in the script and took 20 minutes for me to explain. (Although it is quite easy if you think about it).
Sep
13
comment Database for mathematical syntax
@3Sphere Such a reference is quite useful if you see a formula in the Internet or in a paper where the author sees no reason to include a syntax definition. So even a lookup with many definitions is great, as one can often tell the right one from the context.
Sep
5
comment Solving $8=x(2(1-\sqrt{5}))+(1-x)(2(1+\sqrt{5}))$
There is a simple way: Just use Wolfram Alpha
Aug
29
comment Reducing the time to calculate Collatz sequences
@Thijs Good point. Thank you!
Aug
29
comment Reducing the time to calculate Collatz sequences
@Qiachu But then, I would need to save all that information. Assume, that I want to test all $n$ in the intervall $[1,1\,000\,000\,000]$ - I would need about 1 GiB just for caching! But otherwise, a good idea.
Aug
8
comment How many real roots are there to $2^x=x^2$?
@Arturo Err, that would make it clearer, but the time for editing is up.
Aug
8
comment How many real roots are there to $2^x=x^2$?
@Arturo This was meant because the answerer stated, that $x = 2, x = 4$ are the only solutions.
Aug
8
comment How many real roots are there to $2^x=x^2$?
Why is $x\approx-0.76666469596212309311$ a solution?
Jul
7
comment Mathematical Career Advice to a young 16 year wannabe mathematician
@sigma.z.1980 It's good to know, that other people have the same opinion as me.
Jun
15
comment All functions $\frac{1}{f\left(y^2f(x)\right)} = \big(f(x)\big)^2\left(\frac{1}{f\left(x^2-y^2\right)} + \frac{2x^2}{f(y)}\right)$
@J. J. Ah, thanks. I didn't read the ${}^+$ in $\mathbb R^+$.
Jun
15
comment All functions $\frac{1}{f\left(y^2f(x)\right)} = \big(f(x)\big)^2\left(\frac{1}{f\left(x^2-y^2\right)} + \frac{2x^2}{f(y)}\right)$
I just spotted a possible mistake: $1/f(0)=f(0)$ does not implies $f(0)=1$. It only implies, that $f(0)\in\{-1,1\}$.
Jun
14
comment Is such a cryptographic system possible?
That's a great article!
Jun
14
comment How to solve this recurrence using generating functions?
@muffel IIRC it's written by Graham, Patashnik and Knuth.
Jun
13
comment How to solve this recurrence using generating functions?
@muffel Concrete Mathematics is an awesom book when it comes to sums and generating functions. Just if you're curios.
Jun
13
comment How to solve this recurrence using generating functions?
@muffel For b) and c) recall that $\sum_{i=0}^ni^2=n(n+1)(2n+1)/6$.
Jun
13
comment Expected value for a random variable
Oh, yes. You're right.
May
28
comment Convert any number to positive. How?
In textbooks, the first one is often written $\lvert x\rvert$.
May
24
comment A question on logic - where intuition can fail
@amWhy: Thanks for finding such a good title.
May
24
comment Modulo operation notation
I would write it exactly like you, but add brackets. So $p(x) = (d(x) + b(x)\bmod w(x))$ but $p(x)\not=d(x)+b(x)\mod w(x)$. Notice also, that the spacing is also different.
May
24
comment How to understand and appreciate the prime number industry?
@Sebastien: I would not trust a prime I bought. It could be, that the vendor also sold it to someone else.