Equivalence (Tableaux)

tableaux

Definition

Equivalence

$$\frac{t:(A\leftrightarrow B)}{\begin{array}{c}t:At:B\\ \mid \\ f:Af:B\end{array}}\frac{f:(A\leftrightarrow B)}{\begin{array}{c}t:Af:B\\ \mid \\ f:At:B\end{array}}$$