orcom

Theorem.

Arguments:

phi (pr), psi (pr),

Assertions:

((phiveepsi)leftrightarrow(psiveephi))

Proof:

Hyp Ref Line Expr
bcon<1((lnotphitopsi)leftrightarrow(lnotpsitophi))
df-or2((phiveepsi)leftrightarrow(lnotphitopsi))
df-or3((psiveephi)leftrightarrow(lnotpsitophi))
1, 2, 3<2bitr4((phiveepsi)leftrightarrow(psiveephi))