Rule of Association/Disjunction/Formulation 2/Reverse Implication

Theorem

 * $\vdash \paren {p \lor \paren {q \lor r} } \impliedby \paren {\paren {p \lor q} \lor r}$

Proof
By definition of $\impliedby$, we prove:


 * $\vdash \paren {\paren {p \lor q} \lor r} \implies \paren {p \lor \paren {q \lor r} }$