cbval2

Theorem.

Arguments:

x (sv), y (sv), z (sv), w (sv), phi (pr), psi (pr),

Distinct variable conditions:

(x, y), (y, z), (z, w), (w, x),

Hypotheses:

(((xeqz)wedge(yeqw))to(phileftrightarrowpsi))
(y bound in psi)
(x bound in psi)
(w bound in phi)
(z bound in phi)

Assertions:

(forallxforallyphileftrightarrowforallzforallwpsi)

Proof:

Hyp Ref Line Expr
Hypo1(((xeqz)wedge(yeqw))to(phileftrightarrowpsi))
2(y bound in psi)
3(x bound in psi)
4(w bound in phi)
5(z bound in phi)
5bv-∀6(z bound in forallyphi)
3bv-∀7(x bound in forallwpsi)
ax17eq8(w bound in (xeqz))
4, 8bv-∧9(w bound in ((xeqz)wedgephi))
ax17eq10(y bound in (xeqz))
2, 10bv-∧11(y bound in ((xeqz)wedgepsi))
1exp12((xeqz)to((yeqw)to(phileftrightarrowpsi)))
12com12i13((yeqw)to((xeqz)to(phileftrightarrowpsi)))
13im.bidian14((yeqw)to(((xeqz)wedgephi)leftrightarrow((xeqz)wedgepsi)))
9, 11, 14cbval15(forally((xeqz)wedgephi)leftrightarrowforallw((xeqz)wedgepsi))
10alan<16(forally((xeqz)wedgephi)leftrightarrow((xeqz)wedgeforallyphi))
8alan<17(forallw((xeqz)wedgepsi)leftrightarrow((xeqz)wedgeforallwpsi))
15, 16, 17>2bitr18(((xeqz)wedgeforallyphi)leftrightarrow((xeqz)wedgeforallwpsi))
18im.bidian19((xeqz)to(forallyphileftrightarrowforallwpsi))
6, 7, 19cbval20(forallxforallyphileftrightarrowforallzforallwpsi)