im.nan

Theorem.

Arguments:

phi (pr), psi (pr),

Assertions:

((phitolnotpsi)leftrightarrowlnot(phiwedgepsi))

Proof:

Hyp Ref Line Expr
df-an1((phiwedgepsi)leftrightarrowlnot(phitolnotpsi))
1conb>i2((phitolnotpsi)leftrightarrowlnot(phiwedgepsi))