MHB Identity Proof: (A-B)-C=A-(B∪C)

AI Thread Summary
To prove the identity (A-B)-C=A-(B∪C), the discussion highlights the use of set identities, specifically A-B=A\bar{B} and \overline{B∪C}=\bar{B}\bar{C}. The proof involves manipulating these identities to show the equivalence. The conversation emphasizes the importance of understanding set operations and their properties, including commutativity and associativity. Participants are encouraged to apply the provided identities to validate the equality. This exploration of set theory identities is crucial for grasping advanced concepts in mathematics.
gicm
Messages
1
Reaction score
0
Show that(A-B)-C=A-(BUC)
 
Physics news on Phys.org
This can be shown using identities on sets. Two identities are: $A-B=A\bar{B}$ and $\overline{B\cup C}=\bar{B}\bar{C}$. Here $\bar{A}$ denotes the complement of $A$, and I skip intersection, i.e., I write $AB$ for $A\cap B$. There are numerous other identities on sets, such as commutativity and associativity of intersection and union, laws involving the empty set and so on. Can you use the ones I provided to prove your equality?
 
I was reading a Bachelor thesis on Peano Arithmetic (PA). PA has the following axioms (not including the induction schema): $$\begin{align} & (A1) ~~~~ \forall x \neg (x + 1 = 0) \nonumber \\ & (A2) ~~~~ \forall xy (x + 1 =y + 1 \to x = y) \nonumber \\ & (A3) ~~~~ \forall x (x + 0 = x) \nonumber \\ & (A4) ~~~~ \forall xy (x + (y +1) = (x + y ) + 1) \nonumber \\ & (A5) ~~~~ \forall x (x \cdot 0 = 0) \nonumber \\ & (A6) ~~~~ \forall xy (x \cdot (y + 1) = (x \cdot y) + x) \nonumber...
I'm taking a look at intuitionistic propositional logic (IPL). Basically it exclude Double Negation Elimination (DNE) from the set of axiom schemas replacing it with Ex falso quodlibet: ⊥ → p for any proposition p (including both atomic and composite propositions). In IPL, for instance, the Law of Excluded Middle (LEM) p ∨ ¬p is no longer a theorem. My question: aside from the logic formal perspective, is IPL supposed to model/address some specific "kind of world" ? Thanks.

Similar threads

Replies
5
Views
5K
Replies
2
Views
1K
Replies
18
Views
2K
Replies
3
Views
129K
Replies
2
Views
2K
Replies
3
Views
2K
Replies
1
Views
2K
Replies
3
Views
2K
Back
Top