1.

Check whether the following propositions is a Tautology or a contradiction. (i) (p ∧ ~q) → (p ∧ q) (ii) [~p ∧ (p ∨ q)] → q (iii) (p →q) ↔ (~p →~q) (iv) [~(p →~q)] ∨ (~ p ↔ q) (v) (~p ∨ q) ↔ (p ∨~9)

Answer»

(i) (p ∧~q) → (p∧q)

pq~q(a) p ∧~q(b) p∧q(a)  (b)
TTFFTT
TFTTFF
FTFFFT
FFTFFT

It is neither Tautology nor contradiction

(ii) [~p ∧ (p ∨ q)] → q

pqp ∨ q~p~p ∧ (p ∨ q)[~p ∧ (p ∨ q)] q
TTTFFT
TFTFFT
FTTTTT
FFFTFT

F From last column we conclude it is a tautology

(iii) (p →q) ↔ (~p →~q)

pqa pq~p~q~p ~qa → b
TTTFFTT
TFFFTTT
FTTTFFF
FFTTTTT

F It is neither a tautology nor contradiction 

(iv) [~(p →~q)] ∨ (~ p ↔ q)

pq~qp ~q~(p~q) a~ p~ p q ba∨b
TTFFTFFT
TFTTFFTT
FTFTFTTT
FFTTFTFF

It is neither tautology nor contradiction 

(v) (~p ∨ q) ↔ (p ∨~q)

pq~q~p ∨ q a~qp ∨~q bab
TTFTFTT
TFFFTTF
FTTTFFF
FFTTTTT

It is neither tautology nor contradiction



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