Theorem sbequ12r 1920

Description: An equality theorem for substitution. (Contributed by NM, 6-Oct-2004.) (Proof shortened by Andrew Salmon, 21-Jun-2011.)

Assertion

Ref	Expression
sbequ12r	|- (x = y -> ([x / y]ph <-> ph))

Proof of Theorem sbequ12r

Step	Hyp	Ref	Expression
1		sbequ12 1919	. . 3 |- (y = x -> (ph <-> [x / y]ph))
2	1	bicomd 192	. 2 |- (y = x -> ([x / y]ph <-> ph))
3	2	equcoms 1681	1 |- (x = y -> ([x / y]ph <-> ph))

Syntax hints:   -> wi 4   <-> wb 176  [wsb 1648

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-11 1746

This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1542  df-sb 1649

This theorem is referenced by:  sbidm  2085  abbi  2463  opeliunxp  4820