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Theorem bj-equsal1 34278
 Description: One direction of equsal 2428. (Contributed by BJ, 30-Sep-2018.)
Hypotheses
Ref Expression
bj-equsal1.1 𝑥𝜓
bj-equsal1.2 (𝑥 = 𝑦 → (𝜑𝜓))
Assertion
Ref Expression
bj-equsal1 (∀𝑥(𝑥 = 𝑦𝜑) → 𝜓)

Proof of Theorem bj-equsal1
StepHypRef Expression
1 bj-equsal1.2 . . . 4 (𝑥 = 𝑦 → (𝜑𝜓))
21a2i 14 . . 3 ((𝑥 = 𝑦𝜑) → (𝑥 = 𝑦𝜓))
32alimi 1813 . 2 (∀𝑥(𝑥 = 𝑦𝜑) → ∀𝑥(𝑥 = 𝑦𝜓))
4 bj-equsal1.1 . . 3 𝑥𝜓
54bj-equsal1ti 34277 . 2 (∀𝑥(𝑥 = 𝑦𝜓) ↔ 𝜓)
63, 5sylib 221 1 (∀𝑥(𝑥 = 𝑦𝜑) → 𝜓)
 Colors of variables: wff setvar class Syntax hints:   → wi 4  ∀wal 1536  Ⅎwnf 1785 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-12 2175  ax-13 2379 This theorem depends on definitions:  df-bi 210  df-an 400  df-ex 1782  df-nf 1786 This theorem is referenced by:  bj-equsal  34280
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