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Theorem foeq3 5104
 Description: Equality theorem for onto functions. (Contributed by NM, 1-Aug-1994.)
Assertion
Ref Expression
foeq3 (𝐴 = 𝐵 → (𝐹:𝐶onto𝐴𝐹:𝐶onto𝐵))

Proof of Theorem foeq3
StepHypRef Expression
1 eqeq2 2049 . . 3 (𝐴 = 𝐵 → (ran 𝐹 = 𝐴 ↔ ran 𝐹 = 𝐵))
21anbi2d 437 . 2 (𝐴 = 𝐵 → ((𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐴) ↔ (𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐵)))
3 df-fo 4908 . 2 (𝐹:𝐶onto𝐴 ↔ (𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐴))
4 df-fo 4908 . 2 (𝐹:𝐶onto𝐵 ↔ (𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐵))
52, 3, 43bitr4g 212 1 (𝐴 = 𝐵 → (𝐹:𝐶onto𝐴𝐹:𝐶onto𝐵))
 Colors of variables: wff set class Syntax hints:   → wi 4   ∧ wa 97   ↔ wb 98   = wceq 1243  ran crn 4346   Fn wfn 4897  –onto→wfo 4900 This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 99  ax-ia2 100  ax-ia3 101  ax-5 1336  ax-gen 1338  ax-4 1400  ax-17 1419  ax-ext 2022 This theorem depends on definitions:  df-bi 110  df-cleq 2033  df-fo 4908 This theorem is referenced by:  f1oeq3  5119  foeq123d  5122  resdif  5148  ffoss  5158
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