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Mirrors > Home > ILE Home > Th. List > neanior | GIF version |
Description: A De Morgan's law for inequality. (Contributed by NM, 18-May-2007.) |
Ref | Expression |
---|---|
neanior | ⊢ ((𝐴 ≠ 𝐵 ∧ 𝐶 ≠ 𝐷) ↔ ¬ (𝐴 = 𝐵 ∨ 𝐶 = 𝐷)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | df-ne 2206 | . . 3 ⊢ (𝐴 ≠ 𝐵 ↔ ¬ 𝐴 = 𝐵) | |
2 | df-ne 2206 | . . 3 ⊢ (𝐶 ≠ 𝐷 ↔ ¬ 𝐶 = 𝐷) | |
3 | 1, 2 | anbi12i 433 | . 2 ⊢ ((𝐴 ≠ 𝐵 ∧ 𝐶 ≠ 𝐷) ↔ (¬ 𝐴 = 𝐵 ∧ ¬ 𝐶 = 𝐷)) |
4 | pm4.56 806 | . 2 ⊢ ((¬ 𝐴 = 𝐵 ∧ ¬ 𝐶 = 𝐷) ↔ ¬ (𝐴 = 𝐵 ∨ 𝐶 = 𝐷)) | |
5 | 3, 4 | bitri 173 | 1 ⊢ ((𝐴 ≠ 𝐵 ∧ 𝐶 ≠ 𝐷) ↔ ¬ (𝐴 = 𝐵 ∨ 𝐶 = 𝐷)) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 ∧ wa 97 ↔ wb 98 ∨ wo 629 = wceq 1243 ≠ wne 2204 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 99 ax-ia2 100 ax-ia3 101 ax-in1 544 ax-in2 545 ax-io 630 |
This theorem depends on definitions: df-bi 110 df-ne 2206 |
This theorem is referenced by: nelpri 3399 0nelop 3985 |
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