Theorem eqsb1 2335

Description: Substitution for the left-hand side in an equality. Class version of equsb3 2004. (Contributed by Rodolfo Medina, 28-Apr-2010.)

Assertion

Ref	Expression
eqsb1	⊢ ([𝑦 / 𝑥]𝑥 = 𝐴 ↔ 𝑦 = 𝐴)

Distinct variable group:   𝑥,𝐴

Allowed substitution hint:   𝐴(𝑦)

Proof of Theorem eqsb1

Dummy variable 𝑤 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		eqsb1lem 2334	. . 3 ⊢ ([𝑤 / 𝑥]𝑥 = 𝐴 ↔ 𝑤 = 𝐴)
2	1	sbbii 1813	. 2 ⊢ ([𝑦 / 𝑤][𝑤 / 𝑥]𝑥 = 𝐴 ↔ [𝑦 / 𝑤]𝑤 = 𝐴)
3		nfv 1576	. . 3 ⊢ Ⅎ𝑤 𝑥 = 𝐴
4	3	sbco2 2018	. 2 ⊢ ([𝑦 / 𝑤][𝑤 / 𝑥]𝑥 = 𝐴 ↔ [𝑦 / 𝑥]𝑥 = 𝐴)
5		eqsb1lem 2334	. 2 ⊢ ([𝑦 / 𝑤]𝑤 = 𝐴 ↔ 𝑦 = 𝐴)
6	2, 4, 5	3bitr3i 210	1 ⊢ ([𝑦 / 𝑥]𝑥 = 𝐴 ↔ 𝑦 = 𝐴)

Syntax hints:   ↔ wb 105   = wceq 1397  [wsb 1810

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-io 716  ax-5 1495  ax-7 1496  ax-gen 1497  ax-ie1 1541  ax-ie2 1542  ax-8 1552  ax-10 1553  ax-11 1554  ax-i12 1555  ax-bndl 1557  ax-4 1558  ax-17 1574  ax-i9 1578  ax-ial 1582  ax-i5r 1583  ax-ext 2213

This theorem depends on definitions:  df-bi 117  df-nf 1509  df-sb 1811  df-cleq 2224

This theorem is referenced by:  pm13.183  2944  eqsbc1  3071