$F_1: P \Rightarrow \neg P\equiv\neg P\vee \neg P\equiv\neg P$

When we put $P\equiv T$ it will $F$

and When we put $P\equiv F$ it will $T$

`It is called contingency.`

Always false called contradiction or unsatisfiable

Always true called valid or tautology

`At least`

one true called satisfiable.

$F_2: (P \Rightarrow \neg P) \lor ( \neg P \Rightarrow P)\equiv\neg P\vee P\equiv T$(Always true)