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Jan
9
reviewed Approve Prove that $ \frac12 < 4\sin^2\left(\frac{\pi}{14}\right) + \frac{1}{4\cos^2\left(\frac{\pi}{7}\right)} < 2 - \sqrt{2} $
Nov
29
awarded  Civic Duty
Oct
27
reviewed No Action Needed Find $a\in\mathbb{N}$ such that $n^4+a$ is not prime $\forall n\in\mathbb{N}$
Oct
23
revised How to change to same units
edited tags
Oct
23
comment Integral of product of two measurable functions
This is essentially a special case of Holder's inequality.
Oct
23
answered Intuition behind product rule of probability
Oct
22
answered Proof of Aristarchus' Inequality
Oct
22
reviewed Approve Polynomial inequality proof
Oct
22
comment Mean value of the image of an exponentiallly distributed time under a smooth curve
$f(t)$ should be $\phi(t)$ in 3.
Oct
22
reviewed Reviewed prove that quadrangle is isosceles trapezoid
Oct
21
comment How prove this $\int_{-\pi}^{+\pi}\cos{(2x)}\cos{(3x)}\cos{(4x)}\cdots\cos{(2005x)}dx>0$
I dont have a solution, just some computation with maple/ WA
Oct
21
comment How prove this $\int_{-\pi}^{+\pi}\cos{(2x)}\cos{(3x)}\cos{(4x)}\cdots\cos{(2005x)}dx>0$
The integral of $\prod_{k=2}^{n}cos(kx)$ seems to be $0$ for values of $n$ congruent to $-1, 0 \mod 4$ and a positive rational fraction of $\pi$ for $1,2\mod 4$
Oct
21
reviewed Approve $x^{y^z}$: is it $x^{(y^z)}$ or $(x^y)^z$?
Oct
20
comment Power series $ \sum_{r=1}^{n}x^{r}=\:?$
Almost surely this has been answered here before
Oct
20
comment $\int_{-\infty}^{\infty} \frac{1}{2\pi} \exp\{ -\frac{1}{2} ((y-x)^2 + x^2) \} dx$
square completion
Oct
20
answered Are there any open mathematical puzzles?
Oct
19
answered Determine $a<0$ such that $\int_a^0 f(x) dx = f(a)$
Oct
18
comment use combinatorial reasoning to calculate $ \sum{\binom{100}{a}\binom{200}{b}\binom{300}{c}}$
To add some reference, this is sometimes known as Vandermonde's convolution
Oct
17
comment How find the minimum of the value of $n$ such $n^2\equiv 1\pmod{1007}$
Am i missing someting? $1$ will do
Oct
16
comment Why do we call it a $\sigma$-algebra?
@Did doesn't make more sense does it? unles they were auto referencing to the Bourbaki trive they are$ even then