>dfor

Theorem.

Arguments:

phi (pr), psi (pr),

Hypotheses:

(lnotphitopsi)

Assertions:

(phiveepsi)

Proof:

Hyp Ref Line Expr
Hypo1(lnotphitopsi)
df-or2((phiveepsi)leftrightarrow(lnotphitopsi))
1, 2bmp<3(phiveepsi)