bv-∃1

Theorem.

Arguments:

y (sv), phi (pr), x (sv),

Dummy variables:

z (sv),

Distinct variable conditions:

(z, y), (z, phi), (z, x),

Hypotheses:

(x bound in phi)

Assertions:

(x bound in _e1yphi)

Proof:

Hyp Ref Line Expr
Hypo1(x bound in phi)
ax102(forally(yeqx)to(forallyforally(phileftrightarrow(yeqz))toforallxforally(phileftrightarrow(yeqz))))
2aleqcom3(forallx(xeqy)to(forallyforally(phileftrightarrow(yeqz))toforallxforally(phileftrightarrow(yeqz))))
bv-∀b4(y bound in forally(phileftrightarrow(yeqz)))
4df-Bvp5(forally(phileftrightarrow(yeqz))toforallyforally(phileftrightarrow(yeqz)))
3, 5rpi326(forallx(xeqy)to(forally(phileftrightarrow(yeqz))toforallxforally(phileftrightarrow(yeqz))))
bv-distvar7(y bound in lnotforallx(xeqy))
bv-distvar8(x bound in lnotforallx(xeqy))
1df-Bvp9(phitoforallxphi)
9ax110(lnotforallx(xeqy)to(phitoforallxphi))
dveeq111(lnotforallx(xeqy)to((yeqz)toforallx(yeqz)))
8, 10, 11fv-bid12(lnotforallx(xeqy)to((phileftrightarrow(yeqz))toforallx(phileftrightarrow(yeqz))))
7, 12fv-alyd13(lnotforallx(xeqy)to(forally(phileftrightarrow(yeqz))toforallxforally(phileftrightarrow(yeqz))))
6, 13casei14(forally(phileftrightarrow(yeqz))toforallxforally(phileftrightarrow(yeqz)))
14df-Bvp15(x bound in forally(phileftrightarrow(yeqz)))
15bv-∃16(x bound in existszforally(phileftrightarrow(yeqz)))
df-∃117(_e1yphileftrightarrowexistszforally(phileftrightarrow(yeqz)))
16, 17bvdef18(x bound in _e1yphi)