How can i show that if Γ∪{φ}⇒ψ and Γ∪{φ}⇒¬ψ then Γ⊨¬φ?
how can i show that if Γ∪{φ}⇒ψ and Γ∪{φ}⇒¬ψ then Γ⊨¬φ ?
how can i show that if
1 Answer
Aug 12, 2018
See explanation...
Explanation:
Given:
Gamma uu { varphi } => psi" " and" "Gamma uu { varphi } => not psi
we can deduce:
Gamma uu { varphi } => (psi ^^ not psi) => ⊥
So:
Gamma |== (varphi => ⊥)
From which we can deduce:
Gamma |== not varphi