Theorem necon4d 2955

Description: Contrapositive inference for inequality. (Contributed by NM, 2-Apr-2007.) (Proof shortened by Andrew Salmon, 25-May-2011.)

Hypothesis

Ref	Expression
necon4d.1	⊢ (𝜑 → (𝐴 ≠ 𝐵 → 𝐶 ≠ 𝐷))

Assertion

Ref	Expression
necon4d	⊢ (𝜑 → (𝐶 = 𝐷 → 𝐴 = 𝐵))

Proof of Theorem necon4d

Step	Hyp	Ref	Expression
1		necon4d.1	. . 3 ⊢ (𝜑 → (𝐴 ≠ 𝐵 → 𝐶 ≠ 𝐷))
2	1	necon2bd 2947	. 2 ⊢ (𝜑 → (𝐶 = 𝐷 → ¬ 𝐴 ≠ 𝐵))
3		nne 2935	. 2 ⊢ (¬ 𝐴 ≠ 𝐵 ↔ 𝐴 = 𝐵)
4	2, 3	imbitrdi 251	1 ⊢ (𝜑 → (𝐶 = 𝐷 → 𝐴 = 𝐵))

Syntax hints:  ¬ wn 3   → wi 4   = wceq 1539   ≠ wne 2931

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 207  df-ne 2932

This theorem is referenced by:  oa00  8565  map0g  8892  epfrs  9737  fin23lem24  10328  abs00  15295  oddvds  19513  01eq0ringOLD  20476  isdomn4  20661  isabvd  20757  uvcf1  21737  lindff1  21765  hausnei2  23276  dfconn2  23342  hausflimi  23903  hauspwpwf1  23910  cxpeq0  26623  his6  31012  fnpreimac  32582  deg1le0eq0  33503  lkreqN  39109  ltrnideq  40115  hdmapip0  41855  sticksstones2  42082  unitscyglem4  42133  rpnnen3  42981