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 8h comment If $f$ is odd how does this imply that $f$ is symmetric about the origin in polar coordinates? Symmetric about the origin is not the same as symmetric about the y-axis, I think this may be the cause for your confusion. 18h comment Topologies on a finite set with the same number of open sets If you apply a permutation to the topology you are going to get a topology homeomorphic to the original one. 18h comment Topologies on a finite set with the same number of open sets What is $|\tau|$? 20h answered The product of $2×653×733×977$ has each digit exactly once except for one, which one is it? 20h comment In how many ways can we select $x$ distinct candies from a collection of $n$ candies of distinct types? I assume the candies from each jar are identical between each other and candies from different jars are distinct, is this assumption correct? 20h answered $\frac{(mn)!}{m!(n!)^m}\in\mathbb N^*$? 1d comment Coloring the windmill Sure, happy to help. Nice drawing by the way. 1d comment Coloring the windmill I think that's why. Is that it, or did you already take that into account? 1d comment Coloring the windmill Did you take this into account: " but observe that in this case the number of orbits is double that of a regular n-polygon because each wing is built from two parts."? Maybe that is the reason. 1d revised Coloring the windmill added 257 characters in body 1d comment Coloring the windmill Is $840$ the correct answer? 1d answered Coloring the windmill 1d answered Let $S$ be a semigroup that satisfies the property $\forall a \in S, aS=S \wedge Sa=S$. Show that $S$ is a group. Oct 5 awarded Favorite Question Oct 4 answered Given a string $ab$ and string length $n$, how can I prove that $|\{ (x,y) : x\text{ is index of } a, y\text{ is index of } b , x < y \}| \le n^2/4$ Oct 4 revised For $1\leq n\leq 100$ how many integers are there such that $\frac{n}{n+1}$ is a repeating decimal? added 2 characters in body Oct 4 comment For $1\leq n\leq 100$ how many integers are there such that $\frac{n}{n+1}$ is a repeating decimal? Oh yeah, thanks. Oct 4 answered For $1\leq n\leq 100$ how many integers are there such that $\frac{n}{n+1}$ is a repeating decimal? Oct 3 comment how to find which edges are in which faces of planar graph? you look at the drawing. Oct 2 answered What is the difference between a Set, a Vector, and, a Vector Space?