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Mirrors > Home > ILE Home > Th. List > nn0o | GIF version |
Description: An alternate characterization of an odd nonnegative integer. (Contributed by AV, 28-May-2020.) (Proof shortened by AV, 2-Jun-2020.) |
Ref | Expression |
---|---|
nn0o | ⊢ ((𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → ((𝑁 − 1) / 2) ∈ ℕ0) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nn0o1gt2 10305 | . 2 ⊢ ((𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → (𝑁 = 1 ∨ 2 < 𝑁)) | |
2 | 1m1e0 8108 | . . . . . . . 8 ⊢ (1 − 1) = 0 | |
3 | 2 | oveq1i 5542 | . . . . . . 7 ⊢ ((1 − 1) / 2) = (0 / 2) |
4 | 2cn 8110 | . . . . . . . 8 ⊢ 2 ∈ ℂ | |
5 | 2ap0 8132 | . . . . . . . 8 ⊢ 2 # 0 | |
6 | 4, 5 | div0api 7834 | . . . . . . 7 ⊢ (0 / 2) = 0 |
7 | 3, 6 | eqtri 2101 | . . . . . 6 ⊢ ((1 − 1) / 2) = 0 |
8 | 0nn0 8303 | . . . . . 6 ⊢ 0 ∈ ℕ0 | |
9 | 7, 8 | eqeltri 2151 | . . . . 5 ⊢ ((1 − 1) / 2) ∈ ℕ0 |
10 | oveq1 5539 | . . . . . . . 8 ⊢ (𝑁 = 1 → (𝑁 − 1) = (1 − 1)) | |
11 | 10 | oveq1d 5547 | . . . . . . 7 ⊢ (𝑁 = 1 → ((𝑁 − 1) / 2) = ((1 − 1) / 2)) |
12 | 11 | eleq1d 2147 | . . . . . 6 ⊢ (𝑁 = 1 → (((𝑁 − 1) / 2) ∈ ℕ0 ↔ ((1 − 1) / 2) ∈ ℕ0)) |
13 | 12 | adantr 270 | . . . . 5 ⊢ ((𝑁 = 1 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → (((𝑁 − 1) / 2) ∈ ℕ0 ↔ ((1 − 1) / 2) ∈ ℕ0)) |
14 | 9, 13 | mpbiri 166 | . . . 4 ⊢ ((𝑁 = 1 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → ((𝑁 − 1) / 2) ∈ ℕ0) |
15 | 14 | ex 113 | . . 3 ⊢ (𝑁 = 1 → ((𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → ((𝑁 − 1) / 2) ∈ ℕ0)) |
16 | 2z 8379 | . . . . . . . 8 ⊢ 2 ∈ ℤ | |
17 | 16 | a1i 9 | . . . . . . 7 ⊢ ((2 < 𝑁 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → 2 ∈ ℤ) |
18 | nn0z 8371 | . . . . . . . 8 ⊢ (𝑁 ∈ ℕ0 → 𝑁 ∈ ℤ) | |
19 | 18 | ad2antrl 473 | . . . . . . 7 ⊢ ((2 < 𝑁 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → 𝑁 ∈ ℤ) |
20 | 2re 8109 | . . . . . . . . . 10 ⊢ 2 ∈ ℝ | |
21 | nn0re 8297 | . . . . . . . . . 10 ⊢ (𝑁 ∈ ℕ0 → 𝑁 ∈ ℝ) | |
22 | ltle 7198 | . . . . . . . . . 10 ⊢ ((2 ∈ ℝ ∧ 𝑁 ∈ ℝ) → (2 < 𝑁 → 2 ≤ 𝑁)) | |
23 | 20, 21, 22 | sylancr 405 | . . . . . . . . 9 ⊢ (𝑁 ∈ ℕ0 → (2 < 𝑁 → 2 ≤ 𝑁)) |
24 | 23 | adantr 270 | . . . . . . . 8 ⊢ ((𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → (2 < 𝑁 → 2 ≤ 𝑁)) |
25 | 24 | impcom 123 | . . . . . . 7 ⊢ ((2 < 𝑁 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → 2 ≤ 𝑁) |
26 | eluz2 8625 | . . . . . . 7 ⊢ (𝑁 ∈ (ℤ≥‘2) ↔ (2 ∈ ℤ ∧ 𝑁 ∈ ℤ ∧ 2 ≤ 𝑁)) | |
27 | 17, 19, 25, 26 | syl3anbrc 1122 | . . . . . 6 ⊢ ((2 < 𝑁 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → 𝑁 ∈ (ℤ≥‘2)) |
28 | simprr 498 | . . . . . 6 ⊢ ((2 < 𝑁 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → ((𝑁 + 1) / 2) ∈ ℕ0) | |
29 | 27, 28 | jca 300 | . . . . 5 ⊢ ((2 < 𝑁 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → (𝑁 ∈ (ℤ≥‘2) ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) |
30 | nno 10306 | . . . . 5 ⊢ ((𝑁 ∈ (ℤ≥‘2) ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → ((𝑁 − 1) / 2) ∈ ℕ) | |
31 | nnnn0 8295 | . . . . 5 ⊢ (((𝑁 − 1) / 2) ∈ ℕ → ((𝑁 − 1) / 2) ∈ ℕ0) | |
32 | 29, 30, 31 | 3syl 17 | . . . 4 ⊢ ((2 < 𝑁 ∧ (𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0)) → ((𝑁 − 1) / 2) ∈ ℕ0) |
33 | 32 | ex 113 | . . 3 ⊢ (2 < 𝑁 → ((𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → ((𝑁 − 1) / 2) ∈ ℕ0)) |
34 | 15, 33 | jaoi 668 | . 2 ⊢ ((𝑁 = 1 ∨ 2 < 𝑁) → ((𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → ((𝑁 − 1) / 2) ∈ ℕ0)) |
35 | 1, 34 | mpcom 36 | 1 ⊢ ((𝑁 ∈ ℕ0 ∧ ((𝑁 + 1) / 2) ∈ ℕ0) → ((𝑁 − 1) / 2) ∈ ℕ0) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 102 ↔ wb 103 ∨ wo 661 = wceq 1284 ∈ wcel 1433 class class class wbr 3785 ‘cfv 4922 (class class class)co 5532 ℝcr 6980 0cc0 6981 1c1 6982 + caddc 6984 < clt 7153 ≤ cle 7154 − cmin 7279 / cdiv 7760 ℕcn 8039 2c2 8089 ℕ0cn0 8288 ℤcz 8351 ℤ≥cuz 8619 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-in1 576 ax-in2 577 ax-io 662 ax-5 1376 ax-7 1377 ax-gen 1378 ax-ie1 1422 ax-ie2 1423 ax-8 1435 ax-10 1436 ax-11 1437 ax-i12 1438 ax-bndl 1439 ax-4 1440 ax-13 1444 ax-14 1445 ax-17 1459 ax-i9 1463 ax-ial 1467 ax-i5r 1468 ax-ext 2063 ax-sep 3896 ax-pow 3948 ax-pr 3964 ax-un 4188 ax-setind 4280 ax-cnex 7067 ax-resscn 7068 ax-1cn 7069 ax-1re 7070 ax-icn 7071 ax-addcl 7072 ax-addrcl 7073 ax-mulcl 7074 ax-mulrcl 7075 ax-addcom 7076 ax-mulcom 7077 ax-addass 7078 ax-mulass 7079 ax-distr 7080 ax-i2m1 7081 ax-0lt1 7082 ax-1rid 7083 ax-0id 7084 ax-rnegex 7085 ax-precex 7086 ax-cnre 7087 ax-pre-ltirr 7088 ax-pre-ltwlin 7089 ax-pre-lttrn 7090 ax-pre-apti 7091 ax-pre-ltadd 7092 ax-pre-mulgt0 7093 ax-pre-mulext 7094 |
This theorem depends on definitions: df-bi 115 df-3or 920 df-3an 921 df-tru 1287 df-fal 1290 df-nf 1390 df-sb 1686 df-eu 1944 df-mo 1945 df-clab 2068 df-cleq 2074 df-clel 2077 df-nfc 2208 df-ne 2246 df-nel 2340 df-ral 2353 df-rex 2354 df-reu 2355 df-rmo 2356 df-rab 2357 df-v 2603 df-sbc 2816 df-dif 2975 df-un 2977 df-in 2979 df-ss 2986 df-pw 3384 df-sn 3404 df-pr 3405 df-op 3407 df-uni 3602 df-int 3637 df-br 3786 df-opab 3840 df-mpt 3841 df-id 4048 df-po 4051 df-iso 4052 df-xp 4369 df-rel 4370 df-cnv 4371 df-co 4372 df-dm 4373 df-rn 4374 df-res 4375 df-ima 4376 df-iota 4887 df-fun 4924 df-fn 4925 df-f 4926 df-fv 4930 df-riota 5488 df-ov 5535 df-oprab 5536 df-mpt2 5537 df-pnf 7155 df-mnf 7156 df-xr 7157 df-ltxr 7158 df-le 7159 df-sub 7281 df-neg 7282 df-reap 7675 df-ap 7682 df-div 7761 df-inn 8040 df-2 8098 df-3 8099 df-4 8100 df-n0 8289 df-z 8352 df-uz 8620 |
This theorem is referenced by: nn0ob 10308 |
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