Theorem equsb3 2460

Description: Substitution applied to an atomic wff. (Contributed by Raph Levien and FL, 4-Dec-2005.) Remove dependency on ax-11 2074. (Revised by Wolf Lammen, 21-Sep-2018.)

Assertion

Ref	Expression
equsb3	⊢ ([𝑥 / 𝑦]𝑦 = 𝑧 ↔ 𝑥 = 𝑧)

Distinct variable group:   𝑦,𝑧

Proof of Theorem equsb3

Dummy variable 𝑤 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		equsb3lem 2459	. . 3 ⊢ ([𝑤 / 𝑦]𝑦 = 𝑧 ↔ 𝑤 = 𝑧)
2	1	sbbii 1944	. 2 ⊢ ([𝑥 / 𝑤][𝑤 / 𝑦]𝑦 = 𝑧 ↔ [𝑥 / 𝑤]𝑤 = 𝑧)
3		sbcom3 2439	. . 3 ⊢ ([𝑥 / 𝑤][𝑤 / 𝑦]𝑦 = 𝑧 ↔ [𝑥 / 𝑤][𝑥 / 𝑦]𝑦 = 𝑧)
4		nfv 1883	. . . 4 ⊢ Ⅎ𝑤[𝑥 / 𝑦]𝑦 = 𝑧
5	4	sbf 2408	. . 3 ⊢ ([𝑥 / 𝑤][𝑥 / 𝑦]𝑦 = 𝑧 ↔ [𝑥 / 𝑦]𝑦 = 𝑧)
6	3, 5	bitri 264	. 2 ⊢ ([𝑥 / 𝑤][𝑤 / 𝑦]𝑦 = 𝑧 ↔ [𝑥 / 𝑦]𝑦 = 𝑧)
7		equsb3lem 2459	. 2 ⊢ ([𝑥 / 𝑤]𝑤 = 𝑧 ↔ 𝑥 = 𝑧)
8	2, 6, 7	3bitr3i 290	1 ⊢ ([𝑥 / 𝑦]𝑦 = 𝑧 ↔ 𝑥 = 𝑧)

Syntax hints:   ↔ wb 196  [wsb 1937

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1762  ax-4 1777  ax-5 1879  ax-6 1945  ax-7 1981  ax-10 2059  ax-12 2087  ax-13 2282

This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-ex 1745  df-nf 1750  df-sb 1938

This theorem is referenced by:  sb8eu  2532  mo3  2536  sb8iota  5896  mo5f  29452  mptsnunlem  33315  wl-equsb3  33467  wl-mo3t  33488  wl-sb8eut  33489  frege55lem1b  38506  sbeqal1  38915