GATE CS 2015: Which Predicate Logic Formula is a Tautology? Q57

Computer Sciences > GATE 2015 SET-2 > Logic

Which one of the following well-formed formulae is a tautology?

∀x∃y R(x, y) ↔ ∃y∀x R(x, y)

(∀x[∃y R(x, y) → S(x, y)]) → ∀x∃y S(x, y)

[∀x∃y(P(x, y) → R(x, y))] ↔ [∀x∃y(¬P(x, y) ∨ R(x, y))]

∀x∀y P(x, y) → ∀x∀y P(y, x)

Correct : c

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