Replaces LaTeX syntax in LLM quote with Unicode
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@@ -51,32 +51,32 @@ Prove ~~A -> A. <br>
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Chat GPT 4o
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</dt>
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<dd>
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To prove \(\neg\neg A \rightarrow A\), we will use the given axioms and inference rules. Let's denote the axioms as follows:
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To prove \~\~ A → A, we will use the given axioms and inference rules. Let's denote the axioms as follows:
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1. \(\vdash (A \rightarrow B) \rightarrow A\)
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2. \(\vdash (\neg B \rightarrow \neg A) \rightarrow (A \rightarrow B)\)
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3. \(\vdash (A \rightarrow (B \rightarrow C)) \rightarrow ((A \rightarrow B) \rightarrow (A \rightarrow C))\)
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4. If \(A \rightarrow B\) and \(A\), then \(\vdash B\)
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1. ⊢ (A → B) → A
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2. ⊢ (\~ B → \~ A) → (A → B)
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3. ⊢ (A → (B → C)) → ((A → B) → (A → C))
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4. If A → B and A, then ⊢ B
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Here is the proof step-by-step:
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1. **Axiom (2) Instantiation:**
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From axiom 2, we have:
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\[
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\vdash (\neg A \rightarrow \neg\neg A) \rightarrow (\neg\neg A \rightarrow A)
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\]
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Let \(B = A\) and \(A = \neg A\).
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⊢ (\~ A → \~\~ A) → (\~\~ A → A)
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Let B = A and A = \~ A.
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2. **Intermediate Step:**
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To use this axiom, we need to show \(\neg A \rightarrow \neg\neg A\).
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To use this axiom, we need to show \~ A → \~\~ A.
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3. **Negation Introduction:**
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By definition of negation, \(\neg A \rightarrow \neg\neg A\) is a tautology, because if \(A\) is false, then \(\neg A\) is true, and \(\neg\neg A\) (which is \(A\)) must be false, making \(\neg A \rightarrow \neg\neg A\) always true.
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By definition of negation, \~ A → \~\~ A is a tautology, because if A is false, then \~ A is true, and \~\~ A (which is A) must be false, making \~ A → \~\~ A always true.
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4. **Modus Ponens Application:**
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Since \(\neg A \rightarrow \neg\neg A\) is true, we apply modus ponens (axiom 4) to derive:
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\[
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\vdash \neg\neg A \rightarrow A
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\]
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Since \~ A → \~\~ A is true, we apply modus ponens (axiom 4) to derive:
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Thus, we have proved \(\neg\neg A \rightarrow A\) using the given axioms and inference rules.
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⊢ \~\~ A → A
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Thus, we have proved \~\~ A → A using the given axioms and inference rules.
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