Theorem ax10lem4 1941

Description: Lemma for ax10 1944. Change bound variable. (Contributed by NM, 8-Jul-2016.)

Assertion

Ref	Expression
ax10lem4	⊢ (∀x x = w → ∀y y = x)

Distinct variable groups:   x,w   y,w

Proof of Theorem ax10lem4

Dummy variable z is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ax10lem1 1936	. . . . . 6 ⊢ (∀x x = w → ∀y y = w)
2		equequ1 1684	. . . . . . . 8 ⊢ (z = x → (z = w ↔ x = w))
3	2	dvelimv 1939	. . . . . . 7 ⊢ (¬ ∀y y = x → (x = w → ∀y x = w))
4		hba1 1786	. . . . . . . . 9 ⊢ (∀y x = w → ∀y∀y x = w)
5		equequ2 1686	. . . . . . . . . 10 ⊢ (x = w → (y = x ↔ y = w))
6	5	sps 1754	. . . . . . . . 9 ⊢ (∀y x = w → (y = x ↔ y = w))
7	4, 6	albidh 1590	. . . . . . . 8 ⊢ (∀y x = w → (∀y y = x ↔ ∀y y = w))
8	7	biimprd 214	. . . . . . 7 ⊢ (∀y x = w → (∀y y = w → ∀y y = x))
9	3, 8	syl6 29	. . . . . 6 ⊢ (¬ ∀y y = x → (x = w → (∀y y = w → ∀y y = x)))
10	1, 9	syl7 63	. . . . 5 ⊢ (¬ ∀y y = x → (x = w → (∀x x = w → ∀y y = x)))
11	10	spsd 1755	. . . 4 ⊢ (¬ ∀y y = x → (∀x x = w → (∀x x = w → ∀y y = x)))
12	11	pm2.43d 44	. . 3 ⊢ (¬ ∀y y = x → (∀x x = w → ∀y y = x))
13	12	com12 27	. 2 ⊢ (∀x x = w → (¬ ∀y y = x → ∀y y = x))
14	13	pm2.18d 103	1 ⊢ (∀x x = w → ∀y y = x)

This proof depends on syntax axioms:  ¬ wn 3   → wi 4   ↔ wb 176  ∀wal 1540

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925

This proof depends on definitions:  df-bi 177  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545

This theorem is used by:  ax10lem5  1942