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Theorem eqeq1dALT 2613
Description: Shorter proof of eqeq1d 2612 based on more axioms. (Contributed by NM, 27-Dec-1993.) (Revised by Wolf Lammen, 19-Nov-2019.) (Proof modification is discouraged.) (New usage is discouraged.)
Hypothesis
Ref Expression
eqeq1d.1 (𝜑𝐴 = 𝐵)
Assertion
Ref Expression
eqeq1dALT (𝜑 → (𝐴 = 𝐶𝐵 = 𝐶))

Proof of Theorem eqeq1dALT
Dummy variable 𝑥 is distinct from all other variables.
StepHypRef Expression
1 eqeq1d.1 . . . . . 6 (𝜑𝐴 = 𝐵)
2 dfcleq 2604 . . . . . 6 (𝐴 = 𝐵 ↔ ∀𝑥(𝑥𝐴𝑥𝐵))
31, 2sylib 207 . . . . 5 (𝜑 → ∀𝑥(𝑥𝐴𝑥𝐵))
4319.21bi 2047 . . . 4 (𝜑 → (𝑥𝐴𝑥𝐵))
54bibi1d 332 . . 3 (𝜑 → ((𝑥𝐴𝑥𝐶) ↔ (𝑥𝐵𝑥𝐶)))
65albidv 1836 . 2 (𝜑 → (∀𝑥(𝑥𝐴𝑥𝐶) ↔ ∀𝑥(𝑥𝐵𝑥𝐶)))
7 dfcleq 2604 . 2 (𝐴 = 𝐶 ↔ ∀𝑥(𝑥𝐴𝑥𝐶))
8 dfcleq 2604 . 2 (𝐵 = 𝐶 ↔ ∀𝑥(𝑥𝐵𝑥𝐶))
96, 7, 83bitr4g 302 1 (𝜑 → (𝐴 = 𝐶𝐵 = 𝐶))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wb 195  wal 1473   = wceq 1475  wcel 1977
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  ax-ext 2590
This theorem depends on definitions:  df-bi 196  df-ex 1696  df-cleq 2603
This theorem is referenced by: (None)
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