If $\alpha$ is a limit ordinal, then $\operatorname{cf}(\alpha)$ is a limit ordinal
21479
Why cofinality is a cardinal.
104190
Can any infinite ordinal be expressed as the sum of a limit ordinal and a finite ordinal?
7507
Proof that $\lim{a_n}=L$ when $n$ goes to infinity, then $\{a_n\}$ its a Cauchy Sequence
154578
Proving there is a sequence convergent to a limit point of a set without axiom of countable choice?
120010
Show that $\aleph_{\alpha}^{\aleph_{1}} = \aleph_{\alpha}^{\aleph_{0}}\cdot 2^{\aleph_1}$
36060
If $\lim_{n\to\infty}x_n=\alpha$, show $\lim_{n\to\infty}(x_1x_2\dots x_n)^{1/n} =\alpha$.
99526
Is $\lim\limits_{n\rightarrow\infty} n$ comparable to $\aleph_0$?
6210
Countable compact spaces as ordinals
156978
First uncountable ordinal
79011
If $(F:E)<\infty$, is it always true that $\operatorname{Aut}(F/E)\leq(F:E)?$
99906
If $f'(c)$ exists then $\lim_{x\to c} f(x)=f(c)$
63618
Can all ordinals be obtained by taking successors and countable limits?
142168
can we a prove ⊢ (α → α) → (α → α)
135941
Derivative of $|x|^\alpha$
76240
How is $\epsilon_0$ countable?
86167
Why are infinite cardinals limit ordinals?
22758
If $\operatorname{ran} F \subseteq \operatorname{dom} G$, then $\operatorname{dom}(G \circ F) = \operatorname{dom} F$.