Tautological Implication and Equivalence Quiz

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Questions and Answers

What is the correct truth table for the implication $p \rightarrow q$?

  • $\begin{array}{c|c} p & q \\ \hline 1 & 1 \\ 1 & 0 \\ 0 & 1 \\ 0 & 0 \end{array}$
  • $\begin{array}{c|c} p & q \\ \hline 0 & 0 \\ 0 & 1 \\ 1 & 0 \\ 1 & 1 \end{array}$
  • $\begin{array}{c|c} p & q \\ \hline 1 & 1 \\ 0 & 1 \\ 0 & 0 \\ 1 & 0 \end{array}$ (correct)
  • $\begin{array}{c|c} p & q \\ \hline 1 & 1 \\ 1 & 0 \\ 1 & 0 \\ 0 & 0 \end{array}$

Which of the following statements is true about the implication $p \rightarrow q$?

  • If $p$ is false, then $q$ can be either true or false. (correct)
  • If $q$ is false, then $p$ must be false.
  • If $p$ is true, then $q$ must be true.
  • If $q$ is true, then $p$ must be true.

Which of the following is the correct truth table for the biconditional $p \leftrightarrow q$?

  • $\begin{array}{c|c} p & q \\ \hline 0 & 0 \\ 0 & 1 \\ 1 & 0 \\ 1 & 1 \end{array}$
  • $\begin{array}{c|c} p & q \\ \hline 1 & 1 \\ 1 & 0 \\ 0 & 1 \\ 0 & 0 \end{array}$
  • $\begin{array}{c|c} p & q \\ \hline 1 & 1 \\ 0 & 0 \\ 0 & 1 \\ 1 & 0 \end{array}$ (correct)
  • $\begin{array}{c|c} p & q \\ \hline 1 & 1 \\ 0 & 1 \\ 1 & 0 \\ 0 & 0 \end{array}$

What is the correct truth table for the negation of the implication $\neg(p \rightarrow q)$?

<p>$\begin{array}{c|c} p &amp; q \ \hline 0 &amp; 1 \ 0 &amp; 0 \ 1 &amp; 1 \ 1 &amp; 0 \end{array}$ (B)</p>
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Which of the following statements is true about the implication $p \rightarrow q$?

<p>If $p$ is false and $q$ is true, then $p \rightarrow q$ is true. (B)</p>
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Which of the following statements is equivalent to the biconditional $p \leftrightarrow q$?

<p>$(p \rightarrow q) \wedge (q \rightarrow p)$ (C)</p>
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What is the purpose of the derivation shown in the example?

<p>To prove that the given statements constitute a valid argument (A)</p>
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What is the main purpose of Theorem 2 in the text?

<p>To prove the validity of the third inference rule (C)</p>
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Which of the following is a tautology?

<p>$A \land B \to C$ (A)</p>
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What is the relationship between the premises and the conclusion in a valid argument?

<p>The premises must imply the conclusion (D)</p>
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What is the purpose of the modus ponens and modus tollens inference rules used in the example?

<p>To derive new formulas from existing ones (B)</p>
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What is the relationship between the statement $A \land B \to C$ and the statement $A \to B \to C$?

<p>They are logically equivalent (B)</p>
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What is the purpose of the third inference rule discussed in the text?

<p>To derive new formulas from existing ones (D)</p>
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What is the relationship between the premises and the conclusion in the example argument?

<p>The premises imply the conclusion (B)</p>
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What is the significance of the equivalence $A \land B \to C \iff A \to B \to C$ in the context of the text?

<p>It is used to prove the validity of the third inference rule (B)</p>
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What is the main logical concept that the text is focused on?

<p>Implication (C)</p>
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Flashcards

Truth table: $p rightarrow q$

The implication $p rightarrow q$ is true in all cases except when $p$ is true and $q$ is false.

$p rightarrow q$ when $p$ is false

If $p$ is false, the implication $p rightarrow q$ is always true regardless of the value of $q$.

Truth table: $p leftrightarrow q$

The biconditional $p leftrightarrow q$ is true when both $p$ and $q$ have the same truth value (both true or both false).

Truth table: $\neg(p \rightarrow q)$

The negation of the implication $\neg(p \rightarrow q)$ is true only when $p$ is true and $q$ is false.

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Biconditional equivalence

The statement $(p \rightarrow q) \wedge (q \rightarrow p)$ is equivalent to the biconditional $p \leftrightarrow q$.

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Valid argument

A valid argument is one where the premises logically guarantee the conclusion.

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Modus ponens/tollens purpose

Modus ponens and modus tollens are inference rules used to derive new formulas from existing ones, based on implications.

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Equivalence: $A \land B \rightarrow C$ and $A \rightarrow (B \rightarrow C)$

The statements $A \land B \rightarrow C$ and $A \rightarrow (B \rightarrow C)$ are logically equivalent.

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Premises and conclusion

In a valid argument, if the premises are true, the conclusion must also be true.

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Study Notes

Tautological Implications and Equivalence

  • A formula is equivalent to a tautology if and only if it is a tautology.
  • A formula is implied by a tautology if and only if it is a tautology.
  • Equivalence of formulas is transitive: if ⇔ and ⇔ then ⇔ .
  • Tautological implication of formulas is also transitive: if ⟹ and ⟹ then ⟹ .

Rules of Inference

  • ∧ ⟹ ; ∧ ⟹
  • ⟹ ∨ ; ⟹ ∨
  • ⟶ ∧ ⟶ ⟹ ⟶
  • ⟶ ∧ ⟶ ∧ ∨ ⟹ ∨
  • ⟶ ∧ ⟶ ∧ ~ ∨ ~ ⟹ ~ ∨ ~

Theorem 1: Equivalence

  • ⟺ if and only if ⟹ and ⟹
  • Proof: ≡ if and only if ⟹ and ⟹

Third Inference Rule

  • Theorem 2: If /, , /- , … , /C and / imply 0, then /, , /- , … , /C imply / ⟶ 0
  • Proof: " ∧ # ∧ … ∧ % ∧ ⟹ 0 then " ∧ # ∧ … ∧ % ⟹ / ⟶ 0

Examples

  • Example 3: Valid argument using Modus ponens and Modus tollens rules of inference.

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