Disjoin antecedents and consequents in a deduction. See orim12dALT for a proof which does not depend on [df-an]. (Contributed by NM, 10-May-1994.)
Disjoin antecedents and consequents in a deduction. See orim12dALT for a proof which does not depend on [df-an]. (Contributed by NM, 10-May-1994.)