In the question whether this statement is a tautology ((A ∨ B) → C)) ≡ ((A → C) ∨ (B → C)) ,
If I take first part ((A ∨ B) → C)) as P and second part ((A → C) ∨ (B → C)) as Q , do I need to prove P-->Q is true? or both P-->Q and Q-->P as true? I am confused about the ≡ symbol.