Theorem ax10 1944

Description: Derive set.mm's original ax-10 2140 from others. (Contributed by NM, 25-Jul-2015.) (Revised by NM, 7-Nov-2015.)

Assertion

Ref	Expression
ax10	⊢ (∀x x = y → ∀y y = x)

Proof of Theorem ax10

Dummy variable z is distinct from all other variables.

Step	Hyp	Ref	Expression
1		ax9v 1655	. 2 ⊢ ¬ ∀z ¬ z = x
2		df-ex 1542	. . 3 ⊢ (∃z z = x ↔ ¬ ∀z ¬ z = x)
3		dveeq2 1940	. . . . . . . 8 ⊢ (¬ ∀y y = x → (z = x → ∀y z = x))
4	3	imp 418	. . . . . . 7 ⊢ ((¬ ∀y y = x ∧ z = x) → ∀y z = x)
5		ax10lem6 1943	. . . . . . . 8 ⊢ (∀x x = y → (∀y z = x → ∀x z = x))
6		equcomi 1679	. . . . . . . . 9 ⊢ (z = x → x = z)
7	6	alimi 1559	. . . . . . . 8 ⊢ (∀x z = x → ∀x x = z)
8	5, 7	syl6 29	. . . . . . 7 ⊢ (∀x x = y → (∀y z = x → ∀x x = z))
9		ax10lem5 1942	. . . . . . 7 ⊢ (∀x x = z → ∀y y = x)
10	4, 8, 9	syl56 30	. . . . . 6 ⊢ (∀x x = y → ((¬ ∀y y = x ∧ z = x) → ∀y y = x))
11	10	exp3acom23 1372	. . . . 5 ⊢ (∀x x = y → (z = x → (¬ ∀y y = x → ∀y y = x)))
12		pm2.18 102	. . . . 5 ⊢ ((¬ ∀y y = x → ∀y y = x) → ∀y y = x)
13	11, 12	syl6 29	. . . 4 ⊢ (∀x x = y → (z = x → ∀y y = x))
14	13	exlimdv 1636	. . 3 ⊢ (∀x x = y → (∃z z = x → ∀y y = x))
15	2, 14	syl5bir 209	. 2 ⊢ (∀x x = y → (¬ ∀z ¬ z = x → ∀y y = x))
16	1, 15	mpi 16	1 ⊢ (∀x x = y → ∀y y = x)

This proof depends on syntax axioms:  ¬ wn 3   → wi 4   ∧ wa 358  ∀wal 1540  ∃wex 1541

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:  aecom  1946  ax10o  1952  axi10  2331