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12h
answered Let $A \subset \mathbb Z^3$ / $|A| < \infty$. Prove that: $|A| \le \sqrt{|A_x| |A_y| |A_z|}$
17h
asked Does $ \sum_{(m,n) \neq (0,0)} \frac{(-1)^{m+n}}{m^2 + n^2} $ have an exact value?
20h
answered Sum: $1-2+3-4+5-6+…$
1d
answered Extending 2-adic valuation to real numbers
Jun
29
answered Is there something between summation and integration?
Jun
28
asked How to derive $\sum_{n=0}^\infty 1 = -\frac{1}{2}$ without zeta regularization
Jun
28
answered What we get if we add 1/2 infinite times
Jun
28
answered Proof $\{(x,y,z)|4x^2+9y^2+16z^2<1\}$ is an open set
Jun
23
answered Arnold Trivium Problem 39
Jun
23
answered Why does $\cos(x) + \cos(y) - \cos(x + y) = 0$ look like an ellipse?
Jun
22
answered What is the connection between the discriminant of a quadratic and the distance formula?
Jun
21
answered Proving $e^x \sin x$ is not uniformly continuous on $[0,\infty)$
Jun
15
answered Expansion coefficients of an orthonormal basis must satisfy $c_n n^{1/2}\to 0$ as $n\to \infty$ for $\sum|c_n|^2$ to converge.
Jun
14
answered Two sets $X,Y \subset [0,1]$ such that $X+Y=[0,2]$
Jun
12
answered Calculate limits without L'Hospital's Rule
Jun
12
answered What do you need to perform Karatsuba multiplication?
Jun
8
answered Functional analysis: Why $|[x,y]|\leq [x,x]^{1/2}[y,y]^{1/2}$
Jun
8
answered Prove that $(div \ w)(p) = \lim \limits_{r\rightarrow 0} \frac{1}{V_n r^n}\int_{S_r(p)} \langle w,\nu \rangle dS$ using Gauss's theorem
Jun
8
answered $T^2=I$ implies $T$ is diagonalizable
Jun
8
answered Limits and Series in Smooth Infinitesimal Analysis