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 Oct 21 asked How do I prove that the following is a presentation of $\mathbb{Z_{35}}$? Sep 21 asked How do I find a (7, 3) parity check code generator matrix? Jul 24 answered Why are the sets $U_x$ disjoint in this proof of the non path-connectedness of the ordered square, $I_0^2$? Jul 22 answered Does anyone understand this proof: If $A$ is closed and bounded $\implies A$ is sequentially compact. Jun 20 asked How does one construct the Galois field extension $GF((2^2)^3)$? Jun 7 asked How do I show that the following is a basis for the weak topology on $X$? May 4 asked Is there an easy proof to this theorem due to Nagata? Nov 18 asked If $H$ and $K$ are subgroups of a group G, and $a, b \in G$. How do I prove the following relations hold? Sep 23 asked How do I show $|\frac{i\overline{z}}{2} - \frac{i}{2}|=|z - 1|?$ May 17 asked Connected spaces: is there a mistake in the example below from James Munkres' Topology? Oct 21 asked How do I show that $\kappa^+ \le 2^\kappa$ for every cardinal $\kappa$? May 6 asked How do I prove that an uncountable subset $S$ of $\mathbb{R}$ has the in-between property? Dec 5 asked What's the difference between saying that there is no cardinal between $\aleph_0$ and $\aleph_1$ as opposed to saying that… Dec 4 answered Why is $\omega$ the smallest $\infty$? Dec 1 asked Is there a number that's right in the middle of this interval $(0, 1)$? Aug 24 asked If $\kappa$ is a cardinal, $\aleph$ is any $\aleph$-number, and if $\kappa\leq\aleph$ then $\kappa$ can be well ordered as well. Aug 18 asked If $a, p$ are cardinals satisfying $2 p = p$ and $a+p=2^p,$ then $a \ge 2^p.$ Aug 14 asked How do you prove the trichotomy law for cardinal numbers? Aug 11 answered How can one prove that the union of two finite sets is again finite, without the use of arithmetic? Aug 11 asked There exists a finite set of natural numbers which isn't a proper subset of any other finite set of natural numbers?