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Theorem keephyp2v 4498
 Description: Keep a hypothesis containing 2 class variables (for use with the weak deduction theorem dedth 4484). (Contributed by NM, 16-Apr-2005.)
Hypotheses
Ref Expression
keephyp2v.1 (𝐴 = if(𝜑, 𝐴, 𝐶) → (𝜓𝜒))
keephyp2v.2 (𝐵 = if(𝜑, 𝐵, 𝐷) → (𝜒𝜃))
keephyp2v.3 (𝐶 = if(𝜑, 𝐴, 𝐶) → (𝜏𝜂))
keephyp2v.4 (𝐷 = if(𝜑, 𝐵, 𝐷) → (𝜂𝜃))
keephyp2v.5 𝜓
keephyp2v.6 𝜏
Assertion
Ref Expression
keephyp2v 𝜃

Proof of Theorem keephyp2v
StepHypRef Expression
1 keephyp2v.5 . . 3 𝜓
2 iftrue 4434 . . . . . 6 (𝜑 → if(𝜑, 𝐴, 𝐶) = 𝐴)
32eqcomd 2807 . . . . 5 (𝜑𝐴 = if(𝜑, 𝐴, 𝐶))
4 keephyp2v.1 . . . . 5 (𝐴 = if(𝜑, 𝐴, 𝐶) → (𝜓𝜒))
53, 4syl 17 . . . 4 (𝜑 → (𝜓𝜒))
6 iftrue 4434 . . . . . 6 (𝜑 → if(𝜑, 𝐵, 𝐷) = 𝐵)
76eqcomd 2807 . . . . 5 (𝜑𝐵 = if(𝜑, 𝐵, 𝐷))
8 keephyp2v.2 . . . . 5 (𝐵 = if(𝜑, 𝐵, 𝐷) → (𝜒𝜃))
97, 8syl 17 . . . 4 (𝜑 → (𝜒𝜃))
105, 9bitrd 282 . . 3 (𝜑 → (𝜓𝜃))
111, 10mpbii 236 . 2 (𝜑𝜃)
12 keephyp2v.6 . . 3 𝜏
13 iffalse 4437 . . . . . 6 𝜑 → if(𝜑, 𝐴, 𝐶) = 𝐶)
1413eqcomd 2807 . . . . 5 𝜑𝐶 = if(𝜑, 𝐴, 𝐶))
15 keephyp2v.3 . . . . 5 (𝐶 = if(𝜑, 𝐴, 𝐶) → (𝜏𝜂))
1614, 15syl 17 . . . 4 𝜑 → (𝜏𝜂))
17 iffalse 4437 . . . . . 6 𝜑 → if(𝜑, 𝐵, 𝐷) = 𝐷)
1817eqcomd 2807 . . . . 5 𝜑𝐷 = if(𝜑, 𝐵, 𝐷))
19 keephyp2v.4 . . . . 5 (𝐷 = if(𝜑, 𝐵, 𝐷) → (𝜂𝜃))
2018, 19syl 17 . . . 4 𝜑 → (𝜂𝜃))
2116, 20bitrd 282 . . 3 𝜑 → (𝜏𝜃))
2212, 21mpbii 236 . 2 𝜑𝜃)
2311, 22pm2.61i 185 1 𝜃
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 209   = wceq 1538  ifcif 4428 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1911  ax-6 1970  ax-7 2015  ax-8 2114  ax-9 2122  ax-ext 2773 This theorem depends on definitions:  df-bi 210  df-an 400  df-or 845  df-ex 1782  df-sb 2070  df-clab 2780  df-cleq 2794  df-clel 2873  df-if 4429 This theorem is referenced by: (None)
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