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Mirrors > Home > ILE Home > Th. List > nndceq | GIF version |
Description: Equality of natural numbers is decidable. Theorem 7.2.6 of [HoTT], p. (varies). For the specific case where 𝐵 is zero, see nndceq0 4531. (Contributed by Jim Kingdon, 31-Aug-2019.) |
Ref | Expression |
---|---|
nndceq | ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → DECID 𝐴 = 𝐵) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nntri3or 6389 | . . 3 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → (𝐴 ∈ 𝐵 ∨ 𝐴 = 𝐵 ∨ 𝐵 ∈ 𝐴)) | |
2 | elirr 4456 | . . . . . . 7 ⊢ ¬ 𝐴 ∈ 𝐴 | |
3 | eleq2 2203 | . . . . . . 7 ⊢ (𝐴 = 𝐵 → (𝐴 ∈ 𝐴 ↔ 𝐴 ∈ 𝐵)) | |
4 | 2, 3 | mtbii 663 | . . . . . 6 ⊢ (𝐴 = 𝐵 → ¬ 𝐴 ∈ 𝐵) |
5 | 4 | con2i 616 | . . . . 5 ⊢ (𝐴 ∈ 𝐵 → ¬ 𝐴 = 𝐵) |
6 | 5 | olcd 723 | . . . 4 ⊢ (𝐴 ∈ 𝐵 → (𝐴 = 𝐵 ∨ ¬ 𝐴 = 𝐵)) |
7 | orc 701 | . . . 4 ⊢ (𝐴 = 𝐵 → (𝐴 = 𝐵 ∨ ¬ 𝐴 = 𝐵)) | |
8 | elirr 4456 | . . . . . . 7 ⊢ ¬ 𝐵 ∈ 𝐵 | |
9 | eleq2 2203 | . . . . . . 7 ⊢ (𝐴 = 𝐵 → (𝐵 ∈ 𝐴 ↔ 𝐵 ∈ 𝐵)) | |
10 | 8, 9 | mtbiri 664 | . . . . . 6 ⊢ (𝐴 = 𝐵 → ¬ 𝐵 ∈ 𝐴) |
11 | 10 | con2i 616 | . . . . 5 ⊢ (𝐵 ∈ 𝐴 → ¬ 𝐴 = 𝐵) |
12 | 11 | olcd 723 | . . . 4 ⊢ (𝐵 ∈ 𝐴 → (𝐴 = 𝐵 ∨ ¬ 𝐴 = 𝐵)) |
13 | 6, 7, 12 | 3jaoi 1281 | . . 3 ⊢ ((𝐴 ∈ 𝐵 ∨ 𝐴 = 𝐵 ∨ 𝐵 ∈ 𝐴) → (𝐴 = 𝐵 ∨ ¬ 𝐴 = 𝐵)) |
14 | 1, 13 | syl 14 | . 2 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → (𝐴 = 𝐵 ∨ ¬ 𝐴 = 𝐵)) |
15 | df-dc 820 | . 2 ⊢ (DECID 𝐴 = 𝐵 ↔ (𝐴 = 𝐵 ∨ ¬ 𝐴 = 𝐵)) | |
16 | 14, 15 | sylibr 133 | 1 ⊢ ((𝐴 ∈ ω ∧ 𝐵 ∈ ω) → DECID 𝐴 = 𝐵) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 ∧ wa 103 ∨ wo 697 DECID wdc 819 ∨ w3o 961 = wceq 1331 ∈ wcel 1480 ωcom 4504 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 603 ax-in2 604 ax-io 698 ax-5 1423 ax-7 1424 ax-gen 1425 ax-ie1 1469 ax-ie2 1470 ax-8 1482 ax-10 1483 ax-11 1484 ax-i12 1485 ax-bndl 1486 ax-4 1487 ax-13 1491 ax-14 1492 ax-17 1506 ax-i9 1510 ax-ial 1514 ax-i5r 1515 ax-ext 2121 ax-sep 4046 ax-nul 4054 ax-pow 4098 ax-pr 4131 ax-un 4355 ax-setind 4452 ax-iinf 4502 |
This theorem depends on definitions: df-bi 116 df-dc 820 df-3or 963 df-3an 964 df-tru 1334 df-nf 1437 df-sb 1736 df-clab 2126 df-cleq 2132 df-clel 2135 df-nfc 2270 df-ne 2309 df-ral 2421 df-rex 2422 df-v 2688 df-dif 3073 df-un 3075 df-in 3077 df-ss 3084 df-nul 3364 df-pw 3512 df-sn 3533 df-pr 3534 df-uni 3737 df-int 3772 df-tr 4027 df-iord 4288 df-on 4290 df-suc 4293 df-iom 4505 |
This theorem is referenced by: nndifsnid 6403 fidceq 6763 unsnfidcex 6808 unsnfidcel 6809 enqdc 7169 nninfsellemdc 13206 |
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