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4h
asked Is $i^i$a real number or not?
Jul
28
comment Why is reminder of $8^{30} / 7$ same as that of $1^{30} / 7$
it's probably better if you learn modular arithmetic, it is all really intuitive,
Jul
25
answered Prove that $\sum_{d|n}\phi(d)=n$ where $\phi$ is the Euler's phi function, $n,c\in\mathbb{N}$
Jul
25
comment Is this function uniformly convex?
Oh, I am living here for a while. Although I'm leaving on monday either way :)
Jul
25
comment Is this function uniformly convex?
Are you in Sant Cugat?
Jul
25
revised What is $k$ so that $\frac {1001\times 1002 \times … \times 2008} {11^k}$ will be an integer?
added 30 characters in body
Jul
25
answered What is $k$ so that $\frac {1001\times 1002 \times … \times 2008} {11^k}$ will be an integer?
Jul
25
comment Possible orders of the elements of the alternating group $A_n$
Does the problem ask specifically for $A_n$ or for some particular value of $n$? I don't think we are going to be able to give a "closed", "concise" answer. Since the final answer is going to depend heavily on the distribution of the primes.
Jul
25
comment Possible orders of the elements of the alternating group $A_n$
Think about cycles, remember the order of a permutation is equal to the least common multiple of the cycle lengths (in the canonical decompositon). A permutation is in $A_n$ if and only if it has an even number of cycles of even length.
Jul
25
comment The learning problem of abstract algebra
the measures of the problems?
Jul
25
comment Number theory with binary quadratic
lets try to keep it at one problem per post please.
Jul
24
comment Applying the sum-of-digits operation to $4444^{4444}$ three times
answer is $7$...
Jul
24
comment Applying the sum-of-digits operation to $4444^{4444}$ three times
Found it here! artofproblemsolving.com/wiki/index.php/1975_IMO_Problems/…
Jul
24
comment Applying the sum-of-digits operation to $4444^{4444}$ three times
This is from an IMO
Jul
24
revised Number of possible unions of a countable number of sets
added 285 characters in body
Jul
24
answered Number of possible unions of a countable number of sets
Jul
24
comment Every open set is the union of net of increasing open sets
do you know what a net is?
Jul
24
comment One divided by infinity is not zero?
We can say $\lim_{n\to \infty}\frac{1}{n}=0$
Jul
24
comment One divided by infinity is not zero?
$\infty$ is not a real number.
Jul
24
comment Is 1 always an element in multiplicative group?
@lulu I think $\mathbb G_T$ is the multiplicative group taken out of another structure, sort of like how you can take the multiplicative group of a ring, by taking all the elements with inverses and leaving the product operation.