Theorem equsb3ALT 2433

Description: Alternate proof of equsb3 2432, shorter but requiring ax-11 2034. (Contributed by Raph Levien and FL, 4-Dec-2005.) (New usage is discouraged.) (Proof modification is discouraged.)

Assertion

Ref	Expression
equsb3ALT	|- ( [ x / y ] y = z <-> x = z )

Distinct variable group:   y, z

Proof of Theorem equsb3ALT

Dummy variable w is distinct from all other variables.

Step	Hyp	Ref	Expression
1		equsb3lem 2431	. . 3 |- ( [ w / y ] y = z <-> w = z )
2	1	sbbii 1887	. 2 |- ( [ x / w ] [ w / y ] y = z <-> [ x / w ] w = z )
3		nfv 1843	. . 3 |- F/ w y = z
4	3	sbco2 2415	. 2 |- ( [ x / w ] [ w / y ] y = z <-> [ x / y ] y = z )
5		equsb3lem 2431	. 2 |- ( [ x / w ] w = z <-> x = z )
6	2, 4, 5	3bitr3i 290	1 |- ( [ x / y ] y = z <-> x = z )

Syntax hints:   <-> wb 196   [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-10 2019  ax-11 2034  ax-12 2047  ax-13 2246

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881

This theorem is referenced by: (None)