Theorem elimhOLD 1077

Description: Obsolete version of elimh 1076 as of 27-Apr-2023. Hypothesis builder for the weak deduction theorem. For more information, see the Weak Deduction Theorem page mmdeduction.html 1076. (Contributed by NM, 26-Jun-2002.) Revised to use the conditional operator. (Revised by BJ, 30-Sep-2019.) (New usage is discouraged.) (Proof modification is discouraged.)

Hypotheses

Ref	Expression
elimhOLD.1	⊢ ((if-(𝜒, 𝜑, 𝜓) ↔ 𝜑) → (𝜒 ↔ 𝜏))
elimhOLD.2	⊢ ((if-(𝜒, 𝜑, 𝜓) ↔ 𝜓) → (𝜃 ↔ 𝜏))
elimhOLD.3	⊢ 𝜃

Assertion

Ref	Expression
elimhOLD	⊢ 𝜏

Proof of Theorem elimhOLD

Step	Hyp	Ref	Expression
1		ifptru 1068	. . . 4 ⊢ (𝜒 → (if-(𝜒, 𝜑, 𝜓) ↔ 𝜑))
2		elimhOLD.1	. . . 4 ⊢ ((if-(𝜒, 𝜑, 𝜓) ↔ 𝜑) → (𝜒 ↔ 𝜏))
3	1, 2	syl 17	. . 3 ⊢ (𝜒 → (𝜒 ↔ 𝜏))
4	3	ibi 269	. 2 ⊢ (𝜒 → 𝜏)
5		elimhOLD.3	. . 3 ⊢ 𝜃
6		ifpfal 1069	. . . 4 ⊢ (¬ 𝜒 → (if-(𝜒, 𝜑, 𝜓) ↔ 𝜓))
7		elimhOLD.2	. . . 4 ⊢ ((if-(𝜒, 𝜑, 𝜓) ↔ 𝜓) → (𝜃 ↔ 𝜏))
8	6, 7	syl 17	. . 3 ⊢ (¬ 𝜒 → (𝜃 ↔ 𝜏))
9	5, 8	mpbii 235	. 2 ⊢ (¬ 𝜒 → 𝜏)
10	4, 9	pm2.61i 184	1 ⊢ 𝜏

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 208  if-wif 1057

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 209  df-an 399  df-or 844  df-ifp 1058

This theorem is referenced by:  con3ALTOLD  1081