# Tagged Questions

Questions about mathematical logic, including model theory, proof theory, computability theory (a.k.a. recursion theory), and non-standard logics. Questions which merely seek to apply logical or formal reasoning to other areas of mathematics should not use this tag. Consider using one of the ...

24 views

26 views

### How to determine value of statement

Given statement $v(x): |x| = 2 \text{ where } x \in A = \{-1, 0, 1, 2, 3, 4\}$. What will value of $\lnot v(x)$ look like?
42 views

### Is this translation correct?

If I say some real numbers are rational it can be denoted in first order logic, $(\exists x)$ $(real(x) \land rational(x))$ Where $real(x)$ - x is a real number. $rational(x)$ - x is a rational ...
23 views

### Formula to calculate Price of Service

I would like some help in elaborating a formula for a service I will be providing, to a retailer's clients. In simple terms I would be payed a 5% percentage over the price of the clients purchase, ...
25 views

### $A,B$ satisfies on the same finite structures implies $A,B$ are logically equivalent?

$A,B$ are two sentences in Predicate Logic, such that for every finite structure $A$ is satisified iff $B$ is satisfied. Prove/ Disprove: $A$, $B$ are logically equivalent. I assume this ...
66 views

### Dual statements involving functors

I know how to construct the dual of a statement concerning objects and morphisms of a category, and understand the duality principle associated, but I am having trouble when various categories and ...
Consider the following system for Hilbert-style deduction: Axioms: $A \rightarrow (B \rightarrow A)$ $(A \rightarrow (B \rightarrow C)) \rightarrow ((A \rightarrow B) \rightarrow (A \rightarrow C))$ ...