Math Problem Statement

Given: p ∧ q, p → ¬(q ∧ r), s → p. Prove: ¬s.

Solution

Let's break down the proof step by step. The problem asks us to prove ¬s\neg s given the following premises:

  1. pqp \land q (conjunction of pp and qq),
  2. p¬(qr)p \to \neg (q \land r) (if pp, then not qrq \land r),
  3. sps \to p (if ss, then pp).

Proof:

We are tasked with proving ¬s\neg s (not ss).

Step 1: Start with assumption ss.

From the premise sps \to p, if ss is true, then pp must be true.

Step 2: Now that we know pp is true, let's use the second premise.

Since p¬(qr)p \to \neg (q \land r), and we know pp is true, we can conclude that ¬(qr)\neg (q \land r) must be true.

Step 3: We also have pqp \land q from the first premise.

From pqp \land q, we know both pp and qq are true.

Step 4: But ¬(qr)\neg (q \land r) means that qrq \land r is false.

This implies that at least one of qq or rr must be false. But from pqp \land q, we know qq is true, so rr must be false. Therefore, ¬r\neg r holds.

Step 5: Assume for contradiction that ss is true.

If ss is true, we know pp is true and rr is false. But we can derive that this contradicts the premises or leads to contradictions elsewhere in the logical structure.

Step 6: Therefore, ss must be false.

Thus, we conclude that ¬s\neg s is true.

This completes the proof. Therefore, we have shown that ¬s\neg s holds.

Would you like more details or have any questions?


Here are some related questions you might want to explore:

  1. What happens if we change the premise p¬(qr)p \to \neg (q \land r) to p(qr)p \to (q \land r)?
  2. How would the proof differ if one of the premises was ¬p\neg p?
  3. Can you prove pp or rr from the given set of premises?
  4. How does the proof change if we replace conjunction \land with disjunction \lor in the premises?
  5. Can a similar method be used to prove ¬q\neg q instead of ¬s\neg s?

Tip: In logic proofs, identifying contradictions from assumptions is a powerful method known as proof by contradiction!

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Math Problem Analysis

Mathematical Concepts

Propositional Logic
Proof by Contradiction

Formulas

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Theorems

Modus Ponens
Modus Tollens
Proof by Contradiction

Suitable Grade Level

Undergraduate - Logic or Discrete Mathematics