Theorem mpdi 42

Description: A nested modus ponens deduction. (Contributed by NM, 16-Apr-2005.) (Proof shortened by O'Cat, 15-Jan-2008.)

Hypotheses

Ref	Expression
mpdi.1	|- ( ps -> ch )
mpdi.2	|- ( ph -> ( ps -> ( ch -> th ) ) )

Assertion

Ref	Expression
mpdi	|- ( ph -> ( ps -> th ) )

Proof of Theorem mpdi

Step	Hyp	Ref	Expression
1		mpdi.1	. . 3 |- ( ps -> ch )
2	1	a1i 9	. 2 |- ( ph -> ( ps -> ch ) )
3		mpdi.2	. 2 |- ( ph -> ( ps -> ( ch -> th ) ) )
4	2, 3	mpdd 40	1 |- ( ph -> ( ps -> th ) )

Syntax hints:   -> wi 4

This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7

This theorem is referenced by:  mpii  43  pm2.43d  49  gencbval  2647  sbcimdv  2879  suctr  4176  tfrlem9  5958  lbzbi  8701  flqeqceilz  9320  ndvdsadd  10331  gcdneg  10373  bj-inf2vnlem2  10766