Theorem necon2abii 2991

Description: Contrapositive inference for inequality. (Contributed by NM, 2-Mar-2007.)

Hypothesis

Ref	Expression
necon2abii.1	⊢ (𝐴 = 𝐵 ↔ ¬ 𝜑)

Assertion

Ref	Expression
necon2abii	⊢ (𝜑 ↔ 𝐴 ≠ 𝐵)

Proof of Theorem necon2abii

Step	Hyp	Ref	Expression
1		necon2abii.1	. . . 4 ⊢ (𝐴 = 𝐵 ↔ ¬ 𝜑)
2	1	bicomi 223	. . 3 ⊢ (¬ 𝜑 ↔ 𝐴 = 𝐵)
3	2	necon1abii 2989	. 2 ⊢ (𝐴 ≠ 𝐵 ↔ 𝜑)
4	3	bicomi 223	1 ⊢ (𝜑 ↔ 𝐴 ≠ 𝐵)

Syntax hints:  ¬ wn 3   ↔ wb 205   = wceq 1541   ≠ wne 2940

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 206  df-ne 2941

This theorem is referenced by:  frxp2  8129  frxp3  8136  locfindis  23033  flimsncls  23489  tsmsgsum  23642  wilthlem2  26570  topdifinffinlem  36223  ismblfin  36524  elnev  43187