Theorem sbi1v 1812

Description: Forward direction of sbimv 1814. (Contributed by Jim Kingdon, 25-Dec-2017.)

Assertion

Ref	Expression
sbi1v	|- ( [ y / x ] ( ph -> ps ) -> ( [ y / x ] ph -> [ y / x ] ps ) )

Distinct variable group:   x, y

Allowed substitution hints:   ph( x, y)   ps( x, y)

Proof of Theorem sbi1v

Step	Hyp	Ref	Expression
1		sb6 1807	. 2 |- ( [ y / x ] ph <-> A. x ( x = y -> ph ) )
2		sb6 1807	. . 3 |- ( [ y / x ] ( ph -> ps ) <-> A. x ( x = y -> ( ph -> ps ) ) )
3		ax-2 6	. . . . 5 |- ( ( x = y -> ( ph -> ps ) ) -> ( ( x = y -> ph ) -> ( x = y -> ps ) ) )
4	3	al2imi 1387	. . . 4 |- ( A. x ( x = y -> ( ph -> ps ) ) -> ( A. x ( x = y -> ph ) -> A. x ( x = y -> ps ) ) )
5		sb2 1690	. . . 4 |- ( A. x ( x = y -> ps ) -> [ y / x ] ps )
6	4, 5	syl6 33	. . 3 |- ( A. x ( x = y -> ( ph -> ps ) ) -> ( A. x ( x = y -> ph ) -> [ y / x ] ps ) )
7	2, 6	sylbi 119	. 2 |- ( [ y / x ] ( ph -> ps ) -> ( A. x ( x = y -> ph ) -> [ y / x ] ps ) )
8	1, 7	syl5bi 150	1 |- ( [ y / x ] ( ph -> ps ) -> ( [ y / x ] ph -> [ y / x ] ps ) )

Syntax hints:   -> wi 4   A.wal 1282   [wsb 1685

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-ia1 104  ax-ia2 105  ax-ia3 106  ax-5 1376  ax-gen 1378  ax-ie1 1422  ax-ie2 1423  ax-8 1435  ax-11 1437  ax-4 1440  ax-17 1459  ax-i9 1463  ax-ial 1467

This theorem depends on definitions:  df-bi 115  df-sb 1686

This theorem is referenced by:  sbimv  1814