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Theorem bj-ssbequ2 31832
 Description: Note that ax-12 2034 is used only via sp 2041. See sbequ2 1869 and stdpc7 1945. (Contributed by BJ, 22-Dec-2020.)
Assertion
Ref Expression
bj-ssbequ2 (𝑥 = 𝑡 → ([𝑡/𝑥]b𝜑𝜑))

Proof of Theorem bj-ssbequ2
Dummy variable 𝑦 is distinct from all other variables.
StepHypRef Expression
1 df-ssb 31809 . . 3 ([𝑡/𝑥]b𝜑 ↔ ∀𝑦(𝑦 = 𝑡 → ∀𝑥(𝑥 = 𝑦𝜑)))
2 sp 2041 . . . . . 6 (∀𝑥(𝑥 = 𝑦𝜑) → (𝑥 = 𝑦𝜑))
32imim2i 16 . . . . 5 ((𝑦 = 𝑡 → ∀𝑥(𝑥 = 𝑦𝜑)) → (𝑦 = 𝑡 → (𝑥 = 𝑦𝜑)))
43alimi 1730 . . . 4 (∀𝑦(𝑦 = 𝑡 → ∀𝑥(𝑥 = 𝑦𝜑)) → ∀𝑦(𝑦 = 𝑡 → (𝑥 = 𝑦𝜑)))
5 pm3.31 460 . . . . 5 ((𝑦 = 𝑡 → (𝑥 = 𝑦𝜑)) → ((𝑦 = 𝑡𝑥 = 𝑦) → 𝜑))
65alimi 1730 . . . 4 (∀𝑦(𝑦 = 𝑡 → (𝑥 = 𝑦𝜑)) → ∀𝑦((𝑦 = 𝑡𝑥 = 𝑦) → 𝜑))
7 19.23v 1889 . . . . 5 (∀𝑦((𝑦 = 𝑡𝑥 = 𝑦) → 𝜑) ↔ (∃𝑦(𝑦 = 𝑡𝑥 = 𝑦) → 𝜑))
8 equviniva 1947 . . . . . . 7 (𝑥 = 𝑡 → ∃𝑦(𝑥 = 𝑦𝑡 = 𝑦))
9 biid 250 . . . . . . . . . . . 12 (𝑥 = 𝑦𝑥 = 𝑦)
10 equcom 1932 . . . . . . . . . . . 12 (𝑡 = 𝑦𝑦 = 𝑡)
119, 10anbi12ci 730 . . . . . . . . . . 11 ((𝑥 = 𝑦𝑡 = 𝑦) ↔ (𝑦 = 𝑡𝑥 = 𝑦))
1211biimpi 205 . . . . . . . . . 10 ((𝑥 = 𝑦𝑡 = 𝑦) → (𝑦 = 𝑡𝑥 = 𝑦))
1312eximi 1752 . . . . . . . . 9 (∃𝑦(𝑥 = 𝑦𝑡 = 𝑦) → ∃𝑦(𝑦 = 𝑡𝑥 = 𝑦))
14 pm3.35 609 . . . . . . . . 9 ((∃𝑦(𝑦 = 𝑡𝑥 = 𝑦) ∧ (∃𝑦(𝑦 = 𝑡𝑥 = 𝑦) → 𝜑)) → 𝜑)
1513, 14sylan 487 . . . . . . . 8 ((∃𝑦(𝑥 = 𝑦𝑡 = 𝑦) ∧ (∃𝑦(𝑦 = 𝑡𝑥 = 𝑦) → 𝜑)) → 𝜑)
1615ancoms 468 . . . . . . 7 (((∃𝑦(𝑦 = 𝑡𝑥 = 𝑦) → 𝜑) ∧ ∃𝑦(𝑥 = 𝑦𝑡 = 𝑦)) → 𝜑)
178, 16sylan2 490 . . . . . 6 (((∃𝑦(𝑦 = 𝑡𝑥 = 𝑦) → 𝜑) ∧ 𝑥 = 𝑡) → 𝜑)
1817ex 449 . . . . 5 ((∃𝑦(𝑦 = 𝑡𝑥 = 𝑦) → 𝜑) → (𝑥 = 𝑡𝜑))
197, 18sylbi 206 . . . 4 (∀𝑦((𝑦 = 𝑡𝑥 = 𝑦) → 𝜑) → (𝑥 = 𝑡𝜑))
204, 6, 193syl 18 . . 3 (∀𝑦(𝑦 = 𝑡 → ∀𝑥(𝑥 = 𝑦𝜑)) → (𝑥 = 𝑡𝜑))
211, 20sylbi 206 . 2 ([𝑡/𝑥]b𝜑 → (𝑥 = 𝑡𝜑))
2221com12 32 1 (𝑥 = 𝑡 → ([𝑡/𝑥]b𝜑𝜑))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ∧ wa 383  ∀wal 1473  ∃wex 1695  [wssb 31808 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-6 1875  ax-7 1922  ax-12 2034 This theorem depends on definitions:  df-bi 196  df-an 385  df-ex 1696  df-ssb 31809 This theorem is referenced by:  bj-ssbid2  31834
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