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Theorem elsb3 2462
 Description: Substitution applied to an atomic membership wff. (Contributed by NM, 7-Nov-2006.) (Proof shortened by Andrew Salmon, 14-Jun-2011.)
Assertion
Ref Expression
elsb3 ([𝑥 / 𝑦]𝑦𝑧𝑥𝑧)
Distinct variable group:   𝑦,𝑧

Proof of Theorem elsb3
Dummy variable 𝑤 is distinct from all other variables.
StepHypRef Expression
1 nfv 1883 . . 3 𝑦 𝑤𝑧
21sbco2 2443 . 2 ([𝑥 / 𝑦][𝑦 / 𝑤]𝑤𝑧 ↔ [𝑥 / 𝑤]𝑤𝑧)
3 nfv 1883 . . . 4 𝑤 𝑦𝑧
4 elequ1 2037 . . . 4 (𝑤 = 𝑦 → (𝑤𝑧𝑦𝑧))
53, 4sbie 2436 . . 3 ([𝑦 / 𝑤]𝑤𝑧𝑦𝑧)
65sbbii 1944 . 2 ([𝑥 / 𝑦][𝑦 / 𝑤]𝑤𝑧 ↔ [𝑥 / 𝑦]𝑦𝑧)
7 nfv 1883 . . 3 𝑤 𝑥𝑧
8 elequ1 2037 . . 3 (𝑤 = 𝑥 → (𝑤𝑧𝑥𝑧))
97, 8sbie 2436 . 2 ([𝑥 / 𝑤]𝑤𝑧𝑥𝑧)
102, 6, 93bitr3i 290 1 ([𝑥 / 𝑦]𝑦𝑧𝑥𝑧)
 Colors of variables: wff setvar class 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-8 2032  ax-10 2059  ax-11 2074  ax-12 2087  ax-13 2282 This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-tru 1526  df-ex 1745  df-nf 1750  df-sb 1938 This theorem is referenced by:  cvjust  2646
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