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Jan
27
answered Euler's theorem (modular arithmetic) for non-coprime integers
Jan
27
comment $\gcd(4n+1, n+2)$ is found in what sense?
@DonLarynx, $n=6\iff n+2=8,4n+1=25\implies(n+2,4n+1)=1$ Not sure why you are interested on a specific value of $n$
Jan
26
comment $\gcd(4n+1, n+2)$ is found in what sense?
@N.F.Taussig, Clearly so.Thanks
Jan
26
answered $\gcd(4n+1, n+2)$ is found in what sense?
Jan
26
answered Why is it that $\frac{\sin 30}{\sin 18}$ is equal to the golden ratio?
Jan
26
answered $ \int \frac{dx}{4x^2-12x+13}$
Jan
26
comment Smallest integer $x$ for which 10 divides $2^{2013} - x$
@Amad27, Observe that $2^{4k+a}-2^a=2^a(16^k-1)\equiv0\pmod{10}$ for $k\ge1$ as $16^k-1$ is divisible by $16-1=15$
Jan
26
comment Smallest integer $x$ for which 10 divides $2^{2013} - x$
@Amad27< On trial, we observe that the last digit $\pmod{10}$ has a cycle $2,4,8,6$ of period $4$. Now $2013\equiv1\pmod4$
Jan
26
answered Smallest integer $x$ for which 10 divides $2^{2013} - x$
Jan
26
answered How can we make this expression small?
Jan
26
comment Study the convergence of $\sum_{n=1}^\infty \frac{(-1)^n \cos^2(n)}{n}$
See math.stackexchange.com/questions/1120480/…
Jan
26
answered convergence of $ \sum_{n=1}^{\infty} (-1)^n \frac{2^n \sin ^{2n}x }{n } $
Jan
26
comment Polynom equality modulo p
@quid, How about the validity of the accepted answer if $X$ is not an integer?
Jan
26
answered Limit involving sum of fourth and 5th powers of Natural numbers
Jan
26
comment Proving a particular divisibility rule for 7
@Ahmed, See also : math.stackexchange.com/questions/328562/…
Jan
25
comment Find how many positive divisors a number has. What would you do?
mathworld.wolfram.com/DivisorFunction.html
Jan
25
comment Among 10 packet each having weight 100grams 1 packet is defective and weight is 90 grams. How to find out the defective one in only one measurement?
mathsisfun.com/puzzles/weighing-10-bags-solution.html
Jan
25
comment Polynom equality modulo p
@quid, $X^4-X=X(X^3-1)$ which is divisible by $X(X-1)$ which is even, right?
Jan
25
comment Find the antiderivative of $(x^2+x+1)^{20}$
@DavidG.Stork, We are not here pass an exam, right? How would you have solved the original problem?
Jan
25
answered How prove $\sin \left( \alpha+\frac{\pi }{n} \right) \cdots \sin \left( \alpha+\frac{n\pi }{n} \right) =-\frac{\sin n\alpha}{2^{n-1}}$?