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Theorem foeq3 5131
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 2065 . . 3 (𝐴 = 𝐵 → (ran 𝐹 = 𝐴 ↔ ran 𝐹 = 𝐵))
21anbi2d 445 . 2 (𝐴 = 𝐵 → ((𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐴) ↔ (𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐵)))
3 df-fo 4935 . 2 (𝐹:𝐶onto𝐴 ↔ (𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐴))
4 df-fo 4935 . 2 (𝐹:𝐶onto𝐵 ↔ (𝐹 Fn 𝐶 ∧ ran 𝐹 = 𝐵))
52, 3, 43bitr4g 216 1 (𝐴 = 𝐵 → (𝐹:𝐶onto𝐴𝐹:𝐶onto𝐵))
Colors of variables: wff set class
Syntax hints:  wi 4  wa 101  wb 102   = wceq 1259  ran crn 4373   Fn wfn 4924  ontowfo 4927
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 103  ax-ia2 104  ax-ia3 105  ax-5 1352  ax-gen 1354  ax-4 1416  ax-17 1435  ax-ext 2038
This theorem depends on definitions:  df-bi 114  df-cleq 2049  df-fo 4935
This theorem is referenced by:  f1oeq3  5146  foeq123d  5149  resdif  5175  ffoss  5185
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