Theorem dedth2v 3708

Description: Weak deduction theorem for eliminating a hypothesis with 2 class variables. Note: if the hypothesis can be separated into two hypotheses, each with one class variable, then dedth2h 3705 is simpler to use. See also comments in dedth 3704. (Contributed by NM, 13-Aug-1999.) (Proof shortened by Eric Schmidt, 28-Jul-2009.)

Hypotheses

Ref	Expression
dedth2v.1	|- (A = if(ph, A, C) -> (ps <-> ch))
dedth2v.2	|- (B = if(ph, B, D) -> (ch <-> th))
dedth2v.3	|- th

Assertion

Ref	Expression
dedth2v	|- (ph -> ps)

Proof of Theorem dedth2v

Step	Hyp	Ref	Expression
1		dedth2v.1	. . 3 |- (A = if(ph, A, C) -> (ps <-> ch))
2		dedth2v.2	. . 3 |- (B = if(ph, B, D) -> (ch <-> th))
3		dedth2v.3	. . 3 |- th
4	1, 2, 3	dedth2h 3705	. 2 |- ((ph /\ ph) -> ps)
5	4	anidms 626	1 |- (ph -> ps)

Syntax hints:   -> wi 4   <-> wb 176   = wceq 1642  ifcif 3663

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-clab 2340  df-cleq 2346  df-clel 2349  df-if 3664

This theorem is referenced by: (None)