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Module 3: Propositional Logic & Proof Techniques.

20222m

The statement (∼P↔Q)∧∼Q(\sim P \leftrightarrow Q) \land \sim Q is true, when

(i) PP : True, QQ : False
(ii) PP : True, QQ : True
(iii) PP : False, QQ : True
(iv) PP : False, QQ : False

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Answer

Correct Option: (i) PP: True, QQ: False

Explanation

Given statement: (∼P↔Q)∧∼Q(\sim P \leftrightarrow Q) \land \sim Q

For the conjunction to be true, both parts must be true:

  1. ∼Q\sim Q is true   ⟹  Q=False\implies Q = \text{False}
  2. (∼P↔Q)(\sim P \leftrightarrow Q) must be true with Q=FalseQ = \text{False}

Biconditional truth condition

A↔BA \leftrightarrow B is true iff AA and BB have same truth value.

So with Q=FalseQ = \text{False}:
∼P↔Q=True  ⟹  ∼P=Q=False  ⟹  P=True\sim P \leftrightarrow Q = \text{True} \implies \sim P = Q = \text{False} \implies P = \text{True}

Verification via Truth Table

PP QQ ∼P\sim P ∼P↔Q\sim P \leftrightarrow Q ∼Q\sim Q (∼P↔Q)∧∼Q(\sim P \leftrightarrow Q) \land \sim Q
T T F F F F
T F F T T T
F T T T F F
F F T F T F

Only row P=T,Q=FP=T, Q=F yields true.

Final Answer

The statement is true exactly when PP is True and QQ is False, i.e., option (i).

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