Theorem frege55lem2b 38190

Description: Lemma for frege55b 38191. Core proof of Proposition 55 of [Frege1879] p. 50. (Contributed by RP, 24-Dec-2019.) (Proof modification is discouraged.)

Assertion

Ref	Expression
frege55lem2b	|- ( x = y -> [ y / z ] z = x )

Proof of Theorem frege55lem2b

Step	Hyp	Ref	Expression
1		frege54cor1b 38188	. 2 |- [ x / z ] z = x
2		frege53b 38184	. 2 |- ( [ x / z ] z = x -> ( x = y -> [ y / z ] z = x ) )
3	1, 2	ax-mp 5	1 |- ( x = y -> [ y / z ] z = x )

Syntax hints:   -> wi 4   [wsb 1880

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-12 2047  ax-13 2246  ax-ext 2602  ax-frege8 38103  ax-frege52c 38182

This theorem depends on definitions:  df-bi 197  df-an 386  df-ex 1705  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-sbc 3436

This theorem is referenced by:  frege55b  38191