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Aug
22
comment Removable and non-removable discontinuity in one function
Just to mention a curious example in the vicinity of this question: $f\colon\mathbb Q\to \mathbb R$, $\frac ab\mapsto\frac1b$ is not continuous anywhere in its domain, but all points in $\mathbb R\setminus \mathbb Q$ are removable discontinuities.
Aug
22
comment A question about leap year
But the Gregorian calendar was not in effect in 1100, 1200, 1300, 1400, and 1500. Not to mention the 10 days skipped when it was introduced ...
Aug
22
answered A false conjecture by Goldbach
Aug
22
answered Proving: $2(n-1)<(n+1)\sqrt{n}$
Aug
22
answered Show there exists an integer $L<m\leq K$ such that $m/n$ is an upper bound but $(m-1)/n$ is not
Aug
22
comment Is there a proven formula for Pisano periods (Fibonacci numbers taken modulo $n$)?
Do you also need the result only for $k\equiv 1,2\pmod 4$? (After all $2^2\mid F_k(3)$ otherwise)
Aug
22
revised Is there a proven formula for Pisano periods (Fibonacci numbers taken modulo $n$)?
added 7 characters in body; edited title
Aug
22
comment Is there a proven formula for Pisano periods (Fibonacci numbers taken modulo $n$)?
First of all you may want to add a "citation needed" at WP
Aug
21
comment Finding the missing digits of $23!$
considering $3$ is of couse redundant if you consider $9$ anyway ...
Aug
21
answered Is it possible to draw this equilateral triangle?
Aug
21
comment Is it possible to draw this equilateral triangle?
Draw any equilateral triangle $ABC$. Then translate $ABC$ by twice the length of $AB$ to obtain $A'B'C'$. Whatever your circle, at least one of $ABC$, $A'B'C'$ does not contain its center in its inside
Aug
21
comment Pick's Theorem on a triangular (or hex) grid
The linear map that maps $1\mapsto 1$ and $\frac{1+\sqrt 3 i}2\mapsto i$ maps the hexagonal lattice to the square lattice, and thereby a primitive triangle of the hexagonal lattice becomes a primitive triangle of the square latice.
Aug
21
answered Is it possible that the inclusion functor does not preserve limits?
Aug
20
comment Characterization of cosine of rational multiples of $\pi$
How about $\exists n:(x+i\sqrt{1-x^2})^n=1$?
Aug
19
comment Partitioning $\mathbb{R}^d$ with two convex sets
I suppose the proof that $2d+1$ is maximal could go like this: Assume we have $>2d+1$ components. Show that $A,B$ must contain a hyperplane each (which are of course parallel). Then show there is a third parallel hyperplane that is common boundary of $A$ and $B$. Then in this hyperplane we have $>2d-1$ components in $d-1$ dimensions ...
Aug
19
revised Partitioning $\mathbb{R}^d$ with two convex sets
added 21 characters in body
Aug
19
answered Partitioning $\mathbb{R}^d$ with two convex sets
Aug
19
comment Bijective Conformal Mapping onto the Open Unit Disc $\mathbb{D}$
Not really. $z\mapsto z^2$ maps the first quadrant to the upper half plane, not to the unit disk.
Aug
19
answered Is the intersection of an infinite family of subspaces of $V$ itself a subspace of $V$?
Aug
19
comment Bijective Conformal Mapping onto the Open Unit Disc $\mathbb{D}$
Do you know the corresponding mapping for the open first quadrant, say? Your $G_\nu$ are readily transformed to that.