Question: Prove each of the following assertions: a. is valid if and only if True . b. For any , False . c.
Prove each of the following assertions:
a. α is valid if and only if True ⊨ α.
b. For any α, False ⊨ α.
c. α ⊨ β if and only if the sentence (α ⇒ β) is valid.
d. α ≡ β if and only if the sentence (α ⇔ β) is valid.
e. α ⊨ β if and only if the sentence (α ∧ ¬β) is unsatisfiable.
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Remember iff in every model in which is true is also true Therefore a is valid if and ... View full answer
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