Peano axioms in FOL - numbers lower than or equal to another
139505
Peano/Presburger axioms - "find" numbers lower or equal than another number
109926
Axiom of Regularity and infinite sequences
17624
Axiom of Choice iff Every set has a choice function
55461
How to prove that if $a$ belongs to $\mathbb R$, such that $0\leq a \leq\epsilon$, then $a = 0$
38242
Explicit bijection between the successor of $\alpha$ and $\alpha$ (infinite ordinal).
49385
Proving $\forall x (A\to B) \to(A \to \forall x B):x\notin \mbox{free}(A)$ in a Hilbert system where it is not an axiom
142315
How does the Axiom of Regularity apply to $A=\{1,2,3\}$?
34045
3 Statements of axiom of choice are equivalent
154356
The "difference" of two ordinals
5105
Alternative definition of $\|f\|_{\infty}$ as the smallest of all numbers of the form $\sup\{|g(x)| : x \in X \}$, where $f = g$ almost everywhere
19924
Uncountable ordinals without power set axiom
76347
Shorter proof for some equvalences
32180
Why is "$A$ unless $B$" equivalent to $A \lor B$?
95759
Lower Semicontinuity Concepts
50235
Numbering theorem-like environments
108045
Show that are logically equivalent
83757
Is the following equivalent to the axiom of choice?