MHB Is the Symmetric Difference Problem Solved?

AI Thread Summary
The discussion revolves around verifying the truth of two statements involving symmetric differences and set operations. The first statement, A Δ (B ∩ C) = (A Δ B) ∩ (A Δ C), can be disproven by considering A as the universal set. The second statement, A ∪ (B Δ C) = (A ∪ B) Δ (A ∪ C), is also refuted under the same assumption. Participants are encouraged to analyze the corresponding Venn diagrams to visualize the relationships between the sets. The conversation emphasizes the importance of understanding set operations in proving or contradicting mathematical statements.
Yankel
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Hello all,

For each of the following statements, I need to say if it is true or not, to prove if it is true or to contradict if not.

1)
\[A\bigtriangleup (B\cap C)=(A\bigtriangleup B)\cap (A\bigtriangleup C)\]

2)
\[A\cup (B\bigtriangleup C)=(A\cup B)\bigtriangleup (A\cup C)\]

Where
\[\bigtriangleup\]

is the symmetric difference.

I do know that:

\[A\bigtriangleup B=(A-B)\cup (B-A)\]

which is:

\[(A\cap B^{C})\cup (B\cap A^{C})\]How do I proceed from here?

Thank you !
 
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Both equations can be refuted by taking $A$ to be the universal set.
 
Is it correct that these are the corresponding Venn diagrams of both sides in the first statement?
(assuming your way, of making A universal).

View attachment 6444
 

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I was reading documentation about the soundness and completeness of logic formal systems. Consider the following $$\vdash_S \phi$$ where ##S## is the proof-system making part the formal system and ##\phi## is a wff (well formed formula) of the formal language. Note the blank on left of the turnstile symbol ##\vdash_S##, as far as I can tell it actually represents the empty set. So what does it mean ? I guess it actually means ##\phi## is a theorem of the formal system, i.e. there is a...
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