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Theorem frege122d 39983
Description: If 𝐹 is a function, 𝐴 is the successor of 𝑋, and 𝐵 is the successor of 𝑋, then 𝐴 and 𝐵 are the same (or 𝐵 follows 𝐴 in the transitive closure of 𝐹). Similar to Proposition 122 of [Frege1879] p. 79. Compare with frege122 40209. (Contributed by RP, 15-Jul-2020.)
Hypotheses
Ref Expression
frege122d.a (𝜑𝐴 = (𝐹𝑋))
frege122d.b (𝜑𝐵 = (𝐹𝑋))
Assertion
Ref Expression
frege122d (𝜑 → (𝐴(t+‘𝐹)𝐵𝐴 = 𝐵))

Proof of Theorem frege122d
StepHypRef Expression
1 frege122d.a . . 3 (𝜑𝐴 = (𝐹𝑋))
2 frege122d.b . . 3 (𝜑𝐵 = (𝐹𝑋))
31, 2eqtr4d 2856 . 2 (𝜑𝐴 = 𝐵)
43olcd 870 1 (𝜑 → (𝐴(t+‘𝐹)𝐵𝐴 = 𝐵))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wo 841   = wceq 1528   class class class wbr 5057  cfv 6348  t+ctcl 14333
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1787  ax-4 1801  ax-5 1902  ax-6 1961  ax-7 2006  ax-9 2115  ax-ext 2790
This theorem depends on definitions:  df-bi 208  df-an 397  df-or 842  df-ex 1772  df-cleq 2811
This theorem is referenced by: (None)
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