Theorem necon2i 3021

Description: Contrapositive inference for inequality. (Contributed by NM, 18-Mar-2007.)

Hypothesis

Ref	Expression
necon2i.1	⊢ (𝐴 = 𝐵 → 𝐶 ≠ 𝐷)

Assertion

Ref	Expression
necon2i	⊢ (𝐶 = 𝐷 → 𝐴 ≠ 𝐵)

Proof of Theorem necon2i

Step	Hyp	Ref	Expression
1		necon2i.1	. . 3 ⊢ (𝐴 = 𝐵 → 𝐶 ≠ 𝐷)
2	1	neneqd 2992	. 2 ⊢ (𝐴 = 𝐵 → ¬ 𝐶 = 𝐷)
3	2	necon2ai 3016	1 ⊢ (𝐶 = 𝐷 → 𝐴 ≠ 𝐵)

Syntax hints:   → wi 4   = wceq 1538   ≠ wne 2987

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 210  df-ne 2988

This theorem is referenced by:  cmpfi  22013  mcubic  25433  cubic2  25434  2sqlem11  26013  zarcmplem  31234  ovoliunnfl  35099  voliunnfl  35101  volsupnfl  35102  mncn0  40083  aaitgo  40106