Theorem keephyp3v 3719

Description: Keep a hypothesis containing 3 class variables. (Contributed by NM, 27-Sep-1999.)

Hypotheses

Ref	Expression
keephyp3v.1	|- (A = if(ph, A, D) -> (rh <-> ch))
keephyp3v.2	|- (B = if(ph, B, R) -> (ch <-> th))
keephyp3v.3	|- (C = if(ph, C, S) -> (th <-> ta))
keephyp3v.4	|- (D = if(ph, A, D) -> (et <-> ze))
keephyp3v.5	|- (R = if(ph, B, R) -> (ze <-> si))
keephyp3v.6	|- (S = if(ph, C, S) -> (si <-> ta))
keephyp3v.7	|- rh
keephyp3v.8	|- et

Assertion

Ref	Expression
keephyp3v	|- ta

Proof of Theorem keephyp3v

Step	Hyp	Ref	Expression
1		keephyp3v.7	. . 3 |- rh
2		iftrue 3669	. . . . . 6 |- (ph -> if(ph, A, D) = A)
3	2	eqcomd 2358	. . . . 5 |- (ph -> A = if(ph, A, D))
4		keephyp3v.1	. . . . 5 |- (A = if(ph, A, D) -> (rh <-> ch))
5	3, 4	syl 15	. . . 4 |- (ph -> (rh <-> ch))
6		iftrue 3669	. . . . . 6 |- (ph -> if(ph, B, R) = B)
7	6	eqcomd 2358	. . . . 5 |- (ph -> B = if(ph, B, R))
8		keephyp3v.2	. . . . 5 |- (B = if(ph, B, R) -> (ch <-> th))
9	7, 8	syl 15	. . . 4 |- (ph -> (ch <-> th))
10		iftrue 3669	. . . . . 6 |- (ph -> if(ph, C, S) = C)
11	10	eqcomd 2358	. . . . 5 |- (ph -> C = if(ph, C, S))
12		keephyp3v.3	. . . . 5 |- (C = if(ph, C, S) -> (th <-> ta))
13	11, 12	syl 15	. . . 4 |- (ph -> (th <-> ta))
14	5, 9, 13	3bitrd 270	. . 3 |- (ph -> (rh <-> ta))
15	1, 14	mpbii 202	. 2 |- (ph -> ta)
16		keephyp3v.8	. . 3 |- et
17		iffalse 3670	. . . . . 6 |- (-. ph -> if(ph, A, D) = D)
18	17	eqcomd 2358	. . . . 5 |- (-. ph -> D = if(ph, A, D))
19		keephyp3v.4	. . . . 5 |- (D = if(ph, A, D) -> (et <-> ze))
20	18, 19	syl 15	. . . 4 |- (-. ph -> (et <-> ze))
21		iffalse 3670	. . . . . 6 |- (-. ph -> if(ph, B, R) = R)
22	21	eqcomd 2358	. . . . 5 |- (-. ph -> R = if(ph, B, R))
23		keephyp3v.5	. . . . 5 |- (R = if(ph, B, R) -> (ze <-> si))
24	22, 23	syl 15	. . . 4 |- (-. ph -> (ze <-> si))
25		iffalse 3670	. . . . . 6 |- (-. ph -> if(ph, C, S) = S)
26	25	eqcomd 2358	. . . . 5 |- (-. ph -> S = if(ph, C, S))
27		keephyp3v.6	. . . . 5 |- (S = if(ph, C, S) -> (si <-> ta))
28	26, 27	syl 15	. . . 4 |- (-. ph -> (si <-> ta))
29	20, 24, 28	3bitrd 270	. . 3 |- (-. ph -> (et <-> ta))
30	16, 29	mpbii 202	. 2 |- (-. ph -> ta)
31	15, 30	pm2.61i 156	1 |- ta

Syntax hints:  -. wn 3   -> 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)