>and

Theorem.

Arguments:

phi (pr), psi (pr),

Assertions:

(phito(psito(phiwedgepsi)))

Proof:

Hyp Ref Line Expr
df-an1((phiwedgepsi)leftrightarrowlnot(phitolnotpsi))
1bi<2(lnot(phitolnotpsi)to(phiwedgepsi))
2exp-pre3(phito(psito(phiwedgepsi)))