4orass2

Theorem.

Arguments:

phi (pr), psi (pr), chi (pr), theta (pr),

Assertions:

(((phiveepsi)vee(chiveetheta))leftrightarrow((phiveechi)vee(thetaveepsi)))

Proof:

Hyp Ref Line Expr
4orass1(((phiveepsi)vee(chiveetheta))leftrightarrow((phiveechi)vee(psiveetheta)))
orcom2((psiveetheta)leftrightarrow(thetaveepsi))
2bi.bldor>3(((phiveechi)vee(psiveetheta))leftrightarrow((phiveechi)vee(thetaveepsi)))
1, 3bitr4(((phiveepsi)vee(chiveetheta))leftrightarrow((phiveechi)vee(thetaveepsi)))