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Theorem sb4b 2054
 Description: Simplified definition of substitution when variables are distinct. (Contributed by NM, 27-May-1997.)
Assertion
Ref Expression
sb4b x x = y → ([y / x]φx(x = yφ)))

Proof of Theorem sb4b
StepHypRef Expression
1 sb4 2053 . 2 x x = y → ([y / x]φx(x = yφ)))
2 sb2 2023 . 2 (x(x = yφ) → [y / x]φ)
31, 2impbid1 194 1 x x = y → ([y / x]φx(x = yφ)))
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 176  ∀wal 1540  [wsb 1648 This theorem was proved from 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 theorem depends on definitions:  df-bi 177  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649 This theorem is referenced by:  nfsb4t  2080  sbcom  2089  sbcom2  2114
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